AGM_CrewInfo update

Rewrote the turret role detection, AGM_Core turret functions were a great inspiration. Should now properly detect role no matter how badly is vehicle configured. Added ffv icon = handgun in circle (tried rifle which was too small, not recognizable). Priority of roles is: driver, gunner, codriver, commander, ffv, cargo.

![New ffv icon](http://i.imgur.com/NuPsood.png)
They probably don't make much sense outside of this.