Update weapon slot info in the database

when #275 and #246 are done, a ``getWeaponSlotInfo()`` method should be implemented for SpacecraftClasses and using its output the info (in the database and when buying a new ship) should look like this:

**Weaponry**:
Gun ports: 4 small
Turret ports: 4 small
Cannon ports: 6 large
Missile ports: 4 medium, 2 small
Torpedo ports: 2 small
