Revert "[FEATURE em-o] Added `Em.O` (shorthand for `Ember.Object.create`"

Core team consensus is that users who want this shorthand functionality
in their own app can easily create this alias.

This reverts commit e5848449c728d01f93176f0de2c9bed533129a78.
Better feature flagging for container-renderables
Update for 1.3.0 Canary
Remove experimental control helper