iOS support orientation changes

When a view with collapsing header was fully expended, scrolling down
and quickly releasing the finger would couse the list to "bounce back".
Since the view can collapse only if its scrollY amount is less then the
scaled touch slop - the view didn't collapse and instead, scroll was
enabled.

closes #661

* [android] Basic implementation of orientation change event and getter

#dasdsa

* [android] Check if fabAnimator is not null

* [android] Add configChanges prop to NavigationActivity in AndroidManifest

* [android] Fix duplicate declaration of onConfigurationChange

* [android] Use EventEmitter class to dispatch orientation change events

* Adds iOS callback for viewWillAppear/didAppear e.t.c.

* Adds in screen events on Android

* Fixed issue with rightButtons getting ignored in preference for empty Screen buttons

* Android screen lifecycle

This commit is contains a few changes and enhancements to the PR made by simon:

* Use getEventEmitter instead of sendNavigatorEvent
* Dispatch willDisappear and didDisappear events when pushing screens
* Dispatch willAppear and didAppear events when popping screen

fixes #800 #797