Add group system

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

SQF/dayz_code/groups/leaveGroup.sqf

@@ -0,0 +1,16 @@
+private "_group";
+_group = units group player;
+
+if (count _group == 1 or (!isNil "dayz_groupLeftThread" && {!scriptDone dayz_groupLeftThread})) exitWith {
+	_this ctrlShow false;
+};
+
+dayz_groupLeft = nil;
+PVDZ_Server_UpdateGroup = [3,player];
+publicVariableServer "PVDZ_Server_UpdateGroup";
+
+dayz_groupLeftThread = [] spawn {
+	//Wait for response from server to confirm group finished updating in DB
+	waitUntil {!isNil "dayz_groupLeft"};	
+	[player] join grpNull;
+};