* [ASTraitCollection] Add missing properties to ASTraitCollection
* ASTraitCollection now completely reflects UITraitCollection
* Add ASContentSizeCategory enum that corresponds to
UIContentSizeCategory and can be used inside a struct.
* * Remove enum ASContentSizeCategory.
* Use __unsafe_unretained UIContentSizeCategory instead of the enum.
* Added ASPrimitiveTraitCollection lifetime test
* Changes requested at code review:
* Restore one of the ASTraitCollection constructors with a deprecation notice.
* Clean up API by the separation of tvOS-specific interfaces.
* Use [NSString -isEqualToString:] for ASPrimitiveContentSizeCategory equality tests for better readability.
* Encapsulate fallback logic for UIContentSizeCategoryUnspecified.
* Fix failing test
