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

TopTabParams are a subset of ScreenParams, moved the properties that
are shared by both classes to BaseScreenParams.
This change was needed to report screen changes properly in ViewPagerScreen

This is needed since some of the data we need to send in the events
can not be serialised and added to a Bundle.