Gallery

Added Gallery functionality to the Orienteering Game.

1. A User can create a gallery per ControlPoint
2. A User can upload Images to the Gallery
3. A User can delete Images in the Gallery
4. The Gallery is displayed on the show page of the route
5. The Gallery is responsive and auto sliding.

Open Questions

1. Is there an other place to display the gallery?


better: `self.gallery.present?`