* [ios, macos] new struct MGLTransition
* [ios] MGLTransition struct moved to MGLTypes.h
* [ios] MGLTransition implemented for style layer properties
* [ios, macos] added support for getting property transitions
* [ios, macos] updated to MGLDurationFromTimeInterval and MGLTimeIntervalFromDuration
* [ios, macos] added transition properties test
* [ios, macos] modified key strings imp
* [ios, macos] The impl for transition properties were changed to public methods
* [ios, macos] Changelog update
* [ios] Fixed layer space formatting
* [core] The name space was fixed for getters that returned TransitionOptions
* [ios, macos] Added rawLayer transition property tests
* [ios] Added a factory method for MGLTransition and transition-related methods to NSValue(MGLAdditions)
* [ios, macos] Copyedited changelog blurbs about transition properties
Replaced the style layer integration tests with unit tests. Test conversion of style values to property values and vice versa, not just round-tripping. Test the initial state and null-resetting of each null-resettable property. Test NSValue additions for style attribute enumerations. Test properties common to all style layer classes. Test MGLStyle’s source and layer collections.
Eviscerated implementations of unavailable style layer properties corresponding to style specification properties that were renamed. Implemented corresponding getters to prevent ivars from being autosynthesized for these unavailable properties.
Added a missing bridging header to the iOS test project.
