Some weapon reorganizing

I started this with the objective of attaching gun models to the ships, but soon I noticed it is not going to be very far before I start rewriting a bunch of weapon related things (I want more flexible weapon mounts, guns tracking targets so they can be mounted on wings, missiles treated as guided projectiles and launchers as weapons...). That might take x months or not be something you want in the game at all, so I'm offering this as a cleanup instead.

Most of gun logic moved to Weapon.cpp.
Rear laser is activated from the view direction: this works in external view as well.
Attach test_gun model at gunmount points (Lanner and Wave don't have mounts at visible location, try Kanara or Natrix)
Split equipset into h/cpp
Misc cleanup.