* Removed topBar.transparent and added transparent color support for topBar.background.color

* fix unit tests

[BREAKING] Call Navigation.events().bindComponent(this) to listen to lifecycle events

This commit introduces breaking changes to the way components listen to RNN events.


Background

Up until now, components could handle navigation events by implemented a set of callbacks:
* componentDidAppear
* componentDidDisappear
* onNavigationButtonPressed
* onSearchBarUpdated
* onSearchBarCancelPressed

While this worked fine for the most part, this was completely broken for HOCs as RNN invoked these methods only on the registered component (top most HOC), leaving it to the user to propagate these events down the HOC chain. See the discussion in #1642 for more details.


Solution

In order to support HOC use case, we're introducing a new api which will let any Component bind itself to receive navigation events:

```js
class LifecycleScreen extends Component {
  constructor(props) {
    super(props);
    this.subscription = Navigation.events().bindComponent(this);
  }

  componentWillUnmount() {
    // The subscription is removed automatically when components unmount, but they can be explicitly removed as well by calling `this.subscription.remove(); `
  }
}
```

It's still the users responsibility to propagate the `componentId` down the HOC chain, but by binding a component to RNN, it will be able to handle events as expected. Multiple components can be bound for the same `componentId`.


Consolidate event names

* onNavigationButtonPressed -> navigationButtonPressed
* onSearchBarUpdated -> searchBarUpdated
* onSearchBarCancelPressed -> searchBarCancelPressed

* add addicional options to tabbar

* fix tests

* [ios11+] Add searchBar option for topBar

* Fix formatting and linter issues

* Add docs about topBar.searchBar

* Fix missing semicolons

* Revert prettier changes

* Add js tests for onSearchBarUpdated to achieve 100% coverage

* Mark searchBar test as :ios: specific