VLCSearchController: Fix the search controller dismissal

This merge request brings a fix to:

• The search controller dismissal, it is now the only view controller dismissed when pressing the menu button on the AppleTV remote.
• The presentViewController method is now called when displaying the search controller instead of just calling the becomeFirstResponder method.

This merge request also brings some cosmectics changes regarding the gestures allowing to present the search controller:

• Both gestures share the same action so they now share the same method called to trigger the presentation of the view controller.

Closes #1528 (closed)