Add location system

[andreiseverin]

In the future versions, can you please add an option to add locations on a map as in ag66 ?
I had to get back to the old client to add some locations to a map.

Special map developer commands

Available when you start a listen server (local server).
agaddloc name - Add a location.
agdelloc name - Delete a location.
aglistloc - List locations.