2.0.0.0-dev55

* Modularity improvements:
  * Session configuration moved to library
  * FormKey logic was moved from Session
  * SessionIdFlags from Session was removed
  * Move Page logic to the Theme module and library
* Created integration module UX
* Created authorization service (Magento_Authz module)
* Fixed bugs:
  * Fixed the issue that prevented a customer group's shopping cart rules from applying properly to prices. The issue occurred when a customer was manually assigned to a customer group and automatic group assignment was enabled.
  * Fixed the bug with schema upgrade scripts not running after installation
  * Fixed the error with a blank page when user tries to get access to a restricted resource via URL (add Secret Key for URL set to "No")