* Add converter for UIBarButtonSystemItem

* Add support for UIBarButtonSystemItem-styled buttons

* Add documentation about systemItem

* V2 overlay skeleton (#2097)

* skeleton

* basic test

* remove useless files

* remove useles files

* semicolon

* refactoring

* rm useless files

* alert dialog more styles

* hot fix

* tests

* e2e with own alert

* fix test

* fix ios e2e

* custom dialog WIP

* WIP

* refactor custom dialog

* fix e2e

* gitignore

* fix js tests

* remove hardcode

* snackbar

* drop FAB for now

* fix test

* readme

* WIP

* ios, tests

* refactoring

* current tab

* android tests

* readme

* current tab index ios

* fix tests

* readme

* test fix

* probabl test fix

* push/pop promise

* tests

* modal

* other

* fix tests

* probably test fix

* readme

* WIP

* ios, tests

* refactoring

* test fix

* probabl test fix

* setTabButton -> has now the property 'label' to change the label of the TabButton

* Add to documentation

* [BugFix] use i instead of 0 to check all TabItems

Add the preview and pop feature

To use the feature you simply call `navigator.push()` but with additional parameter `previewViewID` which is a React Node.

```js
<TouchableOpacity
  onPressIn={() => this.props.navigator.push({
    screen: 'screenid',
    previewView: this.viewRef,
    previewActions: [{
      title: 'Foo',
      style: 'selected', // none, selected, destructive
      actions: [{ title: 'Bar' }],
    }],
 })
/>
```

This commit saves navBar component props in propsRegistry and restores the saved props
when the component is mounted, allowing us to pass unserializable props to custom navBar component.

This fixes a bug where navigator-level styles could override styles on a specific button.

This pull request allows you to disable the open gesture only in one side of the drawer.

```
Navigation.startSingleScreenApp({
      screen: initialScreen,
      drawer: {
        left: {
          screen: DRAWER_SCREEN,
          disableOpenGesture: false,
        },
        right: {
          screen: SIDEBAR_FILTER_SCREEN,
          disableOpenGesture: true,
        },
      },
    });
```

If we pass disableOpenGesture to the drawer root object, like this: 

```
Navigation.startSingleScreenApp({
      screen: initialScreen,
      drawer: {
        left: {
          screen: DRAWER_SCREEN,
          disableOpenGesture: false,
        },
        right: {
          screen: SIDEBAR_FILTER_SCREEN,
          disableOpenGesture: true,
        },
        disableOpenGesture: true <======
      },
    });
```

Then the two drawer positions would be gesture disabled and the specific disableOpenGesture would be ignored. This way we don`t introduce breaking changes.

This reverts commit 9f2f15bc4f.

* Support iOS 11 prefersLargeTitles #1643

* better and more simple version checking and setting

This commit applies the save props mechanism used when pushing screen
to navigator buttons as well, enabling us to pass unserializable props to buttons.

* throwing an error instead of a string

* return a callback to remove the register handler

Fix props loading from PropsRegistry in custom buttons