1652 [firebase_analytics]bump min flutter version to 1.5.0 and add type params to invokeMethod… (cla: yes, flutterfire)

1653 [shared_preferences] Updated Gradle tooling to match Android Studio 3.4. (cla: yes)

1654 [path_provider] Cast NSInteger to long (cla: yes)

1655 [firebase_auth] add type parameters for invokeMethod and bump min flutter version to 1.5.0 (cla: yes)

1656 Fixes merge conflict in shared_preferences release of 0.5.2+2 (cla: yes)

1657 [firebase_core] replace invokeMethod with invokeMapMethod, add type parameters to invokeMethod calls,  bump min Flutter version to 1.5.0 (cla: yes)