Feature: Admin set a map rotation (or update it).

[LeventHAN]

What I have in mind is:
20 layers for the rotation.

• First layer grab by .getNextMap()
• The other 18 layers will be randomly selected.
• The last one will be a box where user can click and add new custom layers. (So the size of the map rotation can go higher or lower)
• The user can drag-and-drop the layers to change the rotation.
• The user can delete layers from rotation by clicking a x in top right corner?
• The user can switch between pre-saved rotations (can also delete the presets).
  -> Backend: Save collections to schema Maprotation.