Feature/logi crew roles

[LordDz]

Added a logistic crew role that players can select in the class list. They can only construct buildings and are armed with a carbine instead of regular weaponary.

This way the squad leader and the assistant can focus on leading a squad together, instead of having the assistant driving across the map building stuff. Maybe we could give the assistant the ability to call in artillery strikes, to take off the workload of the squad leader.

But the biggest reason for this feature, is that that logi players no longer have to ask squad leaders for the assistant role. The squad leader may not know how to accept a request, or they're busy in the game menu where the request isn't visible or they just don't understand english.

Currently there's a test map with the logi role added for the US nation, but more could be added later for the other nations.

[LordDz]

On hold for now but can be focused on again if requested.