[BUGFIX beta] When selecting controller for view prioritize controllerName over
controller matching template or route name
[BUGFIX beta] Preserve ability to render alternate controller matching template if
controllerName is specified.

Controller precendence for render is as follows:
* explicitly passed controller always has top precedence
* if name explicitly passed, prioritize name over controllerName
* prioritize controllerName when no explicit name
* fall back on routeName
Merge pull request #4532 from ghedamat/controllerName-priority-fix

[BUGFIX] When selecting controller for view prioritize controllerName over controller matching template or route name
[FEATURE property-brace-expansion-improvement]
Merge pull request #4617 from gordonkristan/brace-expansion-improvement

[FEATURE property-brace-expansion-improvement] Potential improvement as per #4605
[FEATURE ember-runtime-proxy-mixin] Add Ember.ProxyMixin.

Moves most functionality of Ember.ObjectProxy into a mixin that use used
for `Ember.ObjectProxy`, but can also be used on its own (for mixin into
custom objects).