Add buyable units

You can now buy a group of two guard units. Ideal for placements in
base.
Cost: 5000
New loading screen
Change sell/buy value on some vehicles, fix bug.

M4A1 now costs 150 and sells for 75
M4A1 CCO now costs 150 and sells for 75
M249 now costs 250 and sells for 125
Mk48 now costs 300 and sells for 150
M240 now costs 300 and sells for 150
Lite / Premium money script fixed, was string instead of int.
Stop timer for money drop

Stop timer for money drop and wait till respawn to start it.
Revert last
Added Briefing Changelog entry
Added air drops, update loading image, fix bugs

Bugged skin for groups are fixed
Removed L85 AWS from spawning (Overpowered)
Added some debug stuff to adminpanel