Fixes #1609

Usage:
    navBarCustomView: 'example.CustomTopBar', // registered component name
    navBarComponentAlignment: 'center' // 'center'/'fill'

* Fix title bar not displayed if it was initially hidden

Also cleaned up VisibilityAnimator.

* Move visibility animator into topBar

* Save titleBarHidden in screenParams when toggling TitleBar

* empty commit

* Dynamic height of collapsing react header

* Add missing class after rebase

This commit adds support for icons in TopTabs.
It’s possible to have icons with text, or only icons.
Use topTabIconColor and selectedTopTabIconColor to color the icons

related to #557 #474 #125

Implement collapsing TopTabs on Android

specify `navBarHideOnScroll: true` in your `TopTabsScreen`

* Move event emmiter logic out of Application

* Implement searchView

Usage:
```js
rightButtons: [
      {
        id: 'searchView',
        label: 'Search',
        hint: 'Search...'
      }
    ]
```

* Translucent TitleBar

* Collapse TopBar

* Less noticeable translucent effect

* Implement ScrollViewDetector

* Collapse on fling

* Collapse on touch up

Complete collapse on touch up instead of fling