Summary:
Introduce ApplicationRef which holds a reference to Application. It exposes a few utility methods to get view roots and activities.
ApplicationInspector has a few template methods for useful things which are not used in this diff and most likely will either be moved/deleted/changed on the final implementation.
Reviewed By: LukeDefeo
Differential Revision: D38829523
fbshipit-source-id: b8aeb133dceb3af42b5f7d6851ef531d35fc7d69