[FEATURE property-brace-expansion-improvement] Enable by default.

Also, updates `Ember.expandProperties` docs.
Merge pull request #5393 from rwjblue/enable-property-brace-expansion-improvement

[FEATURE property-brace-expansion-improvement] Enable by default.
Add a checkbox to raise on deprecation to the tests
Merge pull request #5396 from mixonic/throw-dep

Add a checkbox to raise on deprecation to the tests