Breaking changes

• Restructured project to manage each subproject independently with CocoaPods. Headers can be imported on a per-subspec basis (#import <FirebaseUI/FirebaseAuthUI.h>), or you can just import the global FirebaseUI header.
• Auth: Email auth has been split out into its own auth provider. To enable or disable email auth, instead of using the boolean flag on FUIAuth, add or remove FUIEmailAuthProvider from the array of providers.

Non-breaking changes

• Auth: Updated translation strings
• Auth: Added FUIAnonymousAuthProvider.
• Auth: Added support for full phone numbers including country code to be autofilled into the PhoneUI auth flow.
• FacebookAuth: Pinned Facebook pods to a version that doesn't break login. See #578.
• Database/Firestore: Fixed a crash that could occur if the collection or table view item count was out-of-sync with the data source item count in the middle of an animation.