[sailfish-browser] Move resource policy handling to UI

Depends on https://github.com/nemomobile/nemo-qml-plugin-policy/pull/5
I think we could have key resources here as well...

```
        Resource {
            id: keysResource
            type: Resource.HeadsetButtons
            optional: true
        }
```

And then elsewhere after ```Permissions``` have...

```
    MediaKey { enabled: keysResource.acquired; key: Qt.Key_MediaTogglePlayPause; onPressed: sendTogglePlay() }
    MediaKey { enabled: keysResource.acquired; key: Qt.Key_MediaPlay; onPressed: sendPlay() }
    MediaKey { enabled: keysResource.acquired; key: Qt.Key_MediaPause; onPressed: sendPause() }
    MediaKey { enabled: keysResource.acquired; key: Qt.Key_MediaStop; onPressed: sendStop() }
    MediaKey { enabled: keysResource.acquired; key: Qt.Key_ToggleCallHangup; onPressed: sendTogglePlay() }

```
Above ```sendPlay(),  sendStop(), sendPause(), and sendTogglePlay()``` doesn't exists yet but I guess we could send these commands to the player.