* Translation mechanism improvements:
  * Translate function ->__() was removed from Magento model interfaces. Global function __() was created
  * Added I18n tools for translation dictionary generation and language package generation
* Configuration improvements:
  * Implemented Magento Config component that allows to create new configuration types in a simple way
  * Improved default/store/website configuration
     * config.xml file is designed to store only default/store/website configuration data
     * concrete store/website configuration is loaded on demand
  * Improved Install, Category, Product, EAV, Customer, Wishlist, PDF, VDE, Currency, Email Template, Crontab, Events, Routes, Modules, Locale, Import/Export, Indexer, Resources configuration segments:
     * Configuration moved to separate files. Some parts are transformed to DI configuration and moved to `di.xml` files
     * New configuration files are validated with XSD
     * Format of the configuration changed to make possible its validation
  * Improved configuration in `widget.xml`, `fieldset.xml`, `persistent.xml` and `install.xml` files:
     * `install.xml` was renamed to `install_wizard.xml`
     * The configuration is validated with XSD
     * Format of the configuration changed to make possible its validation
     * Some parts are transformed to DI configuration and moved to `di.xml` files
  * Removed `jstranslate.xml` files and moved all message definitions to `Magento_Core_Helper_Js`.
  * List of non-structured nodes from config.xml were transformed into DI configuration
* JavaScript improvements:
  * Prototype.js usages converted to jQuery:
     * Deprecated prototype.js based method removed from app/code/Magento/Weee/view/frontend/tax-toggle.js
     * Removed deprecated prototype.js based file: app/code/Magento/Checkout/view/frontend/opcheckout.js
     * Updated to use jQuery redirectUrl widget vs prototype based solution:
       * app/code/Magento/Oauth/view/adminhtml/authorize/form/login.phtml
       * app/code/Magento/Oauth/view/frontend/authorize/form/login.phtml
       * app/code/Magento/Catalog/view/frontend/product/list.phtml
  * Removed file containing jQuery that did not meet the Magento 2 coding standard. Replaced with redirect-url widget
     * app/code/Magento/Catalog/view/frontend/js/mage-attributes-processing.js
  * Updated to meet Magento 2 coding standard: app/code/Magento/Checkout/view/frontend/cart/item/default.phtml
  * Added jQuery widgets:
    * mage.deletableItem - Widget to tag DOM element as deletable, by default on click
    * mage.fieldsetControls & mage.fieldsetResetControl - Widget to easily reset a subset of form fields with a reset ui control
    * mage.itemTable  - Widget to easily add a data template block dynamically on an event, by default click.
    * mage.redirectUrl - Simple widget to allow for consistent javascript based redirects that meet the Magento 2 coding standard
    * Added new validation rules for validation widget: 'required-if-not-specified', 'required-if-specified', and 'validate-item-quantity'
* Various improvements:
  * Changed VendorName from Mage to Magento
  * Implemented PSR-0 and PSR-1 Coding Standards
    * All Magento source code has been converted.
    * Tests have been written to enforce PSR-0 and PSR-1 coding standards.
  * Removed empty module setup models. Core resource setup model is used as a default setup model now. Custom setup model must be injected via DI configuration
  * Removed some events (plugins must be used instead):
    * adminhtml_widget_container_html_before
    * admin_session_user_logout
    * model_config_data_save_before
    * admin_system_config_section_save_after
    * backend_menu_load_after
    * catalog_controller_category_init_before
    * catalog_helper_output_construct
    * catalog_controller_product_init
    * catalog_category_tree_move_before
    * catalog_category_tree_move_after
    * catalog_product_website_update_before
    * catalog_product_website_update
    * catalog_product_media_save_before
    * catalog_product_media_add_image
    * catalog_product_type_grouped_price
    * catalog_product_collection_load_before
    * catalogsearch_index_process_start
    * catalogsearch_index_process_complete
    * cms_page_get_available_statuses
    * cms_wysiwyg_config_prepare
    * application_clean_cache
    * theme_copy_after
    * customer_registration_is_allowed
    * log_log_clean_before
    * log_log_clean_after
    * sales_convert_quote_payment_to_order_payment
    * sales_convert_quote_item_to_order_item
    * sales_quote_config_get_product_attributes
  * Removed the Poll module including references and dependencies to/on it.
* Redesign and reimplementation of web services framework
  * Removed the Api module and all existing SOAP V1, SOAP V2, and XML-RPC web services code
  * Implemented new web services framework to support both REST and SOAP based off of a common service interface
  * Implemented a 2-legged OAuth 1.0a based authentication mechanism for both REST and SOAP API calls
* Layout improvements:
  * Arbitrary handle name moved to handle node, id attribute
  * New arguments format, which introduce argument types implemented
  * Translation specified just on the level of node which is going to be translated
  * XSD validation for Layouts XML added
  * Referential integrity check with XSD introduced
  * Added ability to update containers via references
  * Type casting for all kind of types (url, option, array and simple types) added
  * Covered introduced argument types with integrity test
  * Types restrictions was implemented
  * Removed access to direct execution of API through layout by removing <action> nodes
  * Implemented ability to declare containers in layout that don't have any specific semantic value
  * Removed handle declaration from layout update files. Name of the file stands for the handle ID and handle's attributes are defined in the root <layout> node
* PHP 5.4 and 5.5 support:
  * Made application compatible with PHP 5.4 and 5.5
  * Removed workarounds for older PHP versions
  * Minimum supported PHP version is set to 5.4.0
* God Class Mage Eliminated
* Fixed bugs:
  * Fixed address field "State/Province" on frontend, which contained "[object Object]" items instead of necessary values
  * Fixed overriding/extending of global plugin configuration in area specific configuration