Change bottom tab bar button image at runtime

Add setSubTitle implementation for iOS + docs

Fix dead link

Create BitmapDrawable using a constructor that actually uses the Resources reference

Some navBar button properties were marked as common by mistake.

fixes #1162

Fix missing import of PropTypes throwing an error on iOS

Docs weren't very clear on how exactly to return additional packages, i.e., as a <ReactPackages> list [Line 65]. 
Also changed MyApplication to MainApplication on line 54 (if that is a default and hasn't been changed by the developer).

Render children and pass props to children
Export SharedElementTransition on iOS
Omit children from passed props

Pass iconInsets for tab icon [iOS]

* Update app title (android)

* Add v2 docs placeholder path