Fixes #1007

* React Native v0.40.0 fixes

* Implement disableIconTint property on Android TitleBarButtons

* Show contextual menu only on Modal, if showing

* Fix crash if font not set in title bar button parameters

* Support custom font in the Menu items.

* Fix check for custom font.

This commit adds support for the following style properties:
titleBarTitleFontFamily - string, font name in assets
titleBarTitleTextCentered - boolean, default is false

* 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