Add group system

Initial commit, not tested in multiplayer yet. Some revisions still left
to do.

SQF/dayz_code/groups/getPlayer.sqf

@@ -0,0 +1,10 @@
+private "_player";
+
+_player = objNull;
+{
+	if (getPlayerUID _x == _this) exitWith {
+		_player = _x;
+	};
+} count allUnits;
+
+_player