CSW - Add primary weapon support

[johnb432]

When merged this pull request will:

• Title.

• Prioritises launcher weapons over primary weapons, as you usually can't select CSW weapons.

• Fix 2 "features":

  • If the loaded magazine had more than 1 round when disassembling and fit in the weapon returned, it would return the loaded ammo count - 1. I believe in practice this never happened, as only the CUP Metis supports being deployed as a weapon.
  • Not all compatible magazines were taken into account when getting vehicle magazines.

• TODO: Add documentation

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[mrschick]

Neat!
Some time ago I figured something like this could be a nice addition to the CSW component, related to the 3CB Faction's tripod-mounted PKM.