2.0.0.0-dev50

* Modularity improvements:
  * Cleavage of Adminhtml module
    * Moved Sales, Catalog, Tax-related logic to respective modules
    * Moved Action, Cache, Ajax, Dashboard, Index, Json, Rating, Sitemap, Survey, UrlRewrite from root of Adminhtml Controller folder
  * View abstraction was moved into library
  * Eliminated dependency in Magento\Data\Form from Magento\Core module
  * Eliminated Magento\Media module
* Themes update:
  * Templates and layout updates are updated in Cms, Contacts, Core, Directory, GoogleCheckout, Page, Payment, PaypalUk, Paypal, Rating, Review, Rss,Sales, Widget modules, old files moved to magento_backup theme
* Layout improvements:
  * Removed page type hierarchy and page fragment types
  * No direct code execution: methods addColumnRender, addRenderer, addToParentGroup usages as action nodes were eliminated
* Fixed bugs:
  * Impossible to add image using WYSIWYG
  * Legacy static test ObsoleteCodeTest::testPhpFiles produced false-positive results
  * Incorrect copyright information