Add /unwarpable command

GMs should use this before going to weird places where their non-GM
buddies might warp to them and get stuck.

src/Player.hpp

@@ -74,6 +74,7 @@ struct Player {
 
     bool notify;
     bool hidden;
+    bool unwarpable;
 
     bool buddiesSynced;
     int64_t buddyIDs[50];