FirebaseUI 5.0.0

Updates FirebaseUI to be compatible with Firebase 5.0.0.

General:

• Moved to source pods. FirebaseUI no longer ships as a binary, but requires static_framework.
• Imports should be changed from importing individual components to just import FirebaseUI.

Database:

• Indexed arrays no longer observe their queries on init. Call the observeQuery method to start query observation.
• Indexed data sources no longer observe their queries on init.
• Indexed data source initializers no longer take table/collection views. These views should instead be passed in in calls to bind(to:).

Auth:

• Made several methods in the base auth view controller public for easier customization.