* Less intrusive collapsing implementation

In order for a screen to implement collapsingTopBar, it had to define
a specific set of style properties such as drawUnderTabBar or
drawUnderNavBar. This commit aims to make implementing collapsingTopBar
less intrusive by inferring these properties from hideTitleBarOnScroll.

This commit introduces a few fixes and changes related to
the collapsingTopBar mechanism.

1. Screens are now drawn under bottomTabs if titleBarHideOnScroll
   is true.

2. TitleBarHideOnScroll can be passed in AppStyle.

3. ScrollView is detected properly after it gets detached due to large
   diff in render.

4. Take BottomTabs height into account when measuring collapsing
   screens.

related to #557 #474 #125

closes #454

* Implement screenBackgroundColor

* Collapse ViewPagerScreen on TopTab select

* 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

closes #21

Can also be set cross app by using titleBarDisabledButtonColor property in appStyle