Carriers can fit drones and lightweight ships

[Blaumeise03]

This does maybe relate to #17. I thought before the database update it was working, but I am not sure. Anyways, the filtering for drones has to be improved/redone. There is currently no way to differenciate between a drone slot and a fighter slot. So sweet will always show both the drone and the fighter market group wenn tapping a drone/fighter slot. But there is no "can fit" attributes for drones or lightweight ships, so they can be fitted into the drone/fighter slot of carriers.

Filtering out lightweight ships shouldn't be hard, since they have special slots. But filtering out drones is more complicated because when the selection list gets filtered, we don't know what kind of slot it is.