* Parse out experiment payload for experimental FIAMs and store it on FIRIAMMessageDefinition
* Fix bugs in parsing experimental payload
* Add nullable experiment payload to FIAM message definition. Add method in FIRExperimenmtController to validate running experiments and call this when new messages are fetched from FIAM backend
* Add and document new ABT methods, update FirebaseInAppMessaging.podspec to depend on ABT
* Clean up deprecated public message initializers, add experiment payload to private initializers
* Activate experiment for experimental messages upon impression
* Clean up activateExperiment API
* Add experimental payload to all message definition initializers
* Add unit test coverage for new ABT methods
* Add test coverage for parsing experimental messages
* Verify experiment payload gets passed to message superclass
* Scripts/style.sh
* Update Podfile for UI test app to include AB Testing SDK
* Add back deprecated initializers for now, these are needed for the test app
* Test for non-nil experiment payload
* Use mutable array directly, better memory usage
* Bump ABTesting podspec version, depend on new ABT in FIAM
* Remove mentions of FIREventOrigins.h
* Remove experiment payload from public API, hide it in private
* Scripts/style.sh
* Fix comment indentation, allow for FIAM to depend on minor version updates of ABTesting
* Move ABTExperimentPayload import to private header
* Add completion handler to FIRExperimentController updateExperimentsWithServiceOrigin:
* Update tests to verify completion handler is called
* Add error param to the completion handler in updateExperimentsWithServiceOrigin:
* Rename error domain for ABT SDK errors, rename method to set CUPs via the user property controller-- it doesn't do anything in the background
* Add back support for updateExperiments method without completion
* Add description for Failed to get conditional user properties error
* Fix string argument warning
* Deprecate updateExperimentsWithServiceOrigin method that doesn't have a completion handler
* Ignore deprecated warning in tests
* Run scripts/styles.sh
Morgan Chen