Add message and graphical icon to warn when MMapper loses sync

[Sebster7]

When MMapper loses sync, it would really help people who don't know the area, and especially newbies who don't know MMapper well, if there was a warning message and a big warning icon on the MMapper GUI indicating that the current position is unknown and MMapper does not know where you are on the map.

(I remember a newbie got really lost when MMapper lost sync and they had to ask for help on narrate as they were using the exits in the MMapper room rather than in the MUME room and they couldn't go the direction they wanted to go...)