groupmarker component restructure

* moved files to f\groupMarkers
* updated code to be more straightforward/readable (removed unnecessary clauses etc.)
* changed existing groupMarkers types: 7: mech_infantry (for IFVs), 8: tanks (was 7), 9: helo (was 8)
* added new groupMarker types: 10: planes, 11: artillery
* added new specialist marker type: 1: uav