Add group system

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

SQF/dayz_code/groups/inviteToGroup.sqf

@@ -0,0 +1,32 @@
+private ["_hasInvite","_invite","_playerList","_recipient","_uid"];
+
+disableSerialization;
+_playerList = findDisplay 80000 displayCtrl 1;
+_uid = _playerList lbData (lbCurSel _playerList);
+_recipient = _uid call dayz_getPlayer;
+
+if (isNull _recipient or player != leader group player or count (units group _recipient) > 1) exitWith {
+	_this ctrlShow false;
+};
+
+_hasInvite = false;
+{
+	if (_x select 1 == _uid) then {
+		_hasInvite = true;
+	};
+} forEach dayz_activeInvites;
+
+if (_hasInvite) exitWith {
+	systemChat localize "STR_EPOCH_INVITE_PENDING";
+};
+
+_invite = [getPlayerUID player,_uid];
+
+//Update locally with change
+dayz_activeInvites set [count dayz_activeInvites,_invite];
+
+//Sync change to all remote machines (less data than sending whole array)
+PVDZ_groupInvite = [true,_invite];
+publicVariableServer "PVDZ_groupInvite";
+
+systemChat format[localize "STR_EPOCH_INVITE_TO",name _recipient];