[BUGFIX beta] Do not use defineProperty on each View instance.
Merge pull request #5523 from rwjblue/do-not-define-property-too-much

[BUGFIX beta] Do not use defineProperty on each View instance.
Cleanup platform
Merge pull request #5528 from krisselden/platform-cleanup

Cleanup platform
Change ENV.MANDATORY_SETTER to FEATURES so it can be compiled out of production builds.
Merge pull request #5529 from krisselden/mandatory-setter-as-feature

Mandatory setter as feature
Pull in LazyValue and ember-metal integration
Use LazyValue in view helper
Remove relative context Handlebars tests
Use LazyValue in log helper
Register and teardown streams
Use LazyValue in bind-attr helper
Use LazyValue in render helper
Use LazyValue in input helper
Use LazyValue in action helper