The code used to retrieve the tiles for the world map was hardcoded
to retrieve the map tiles via s3. However, non-maingrid servers
do not necessarily publish their map tiles to s3.
The URL was in the form http://map.secondlife.com.s3.amazonaws.com/map-<level>-<x>-<y>-objects.jpg
This change removes the hard coding and places the default s3 URL in the settings.xml file via MapServerURL.
Login retrieves the specific grids URL via a map-server-url option. The url is still expected to
contain jpegs named like map-<level>-<x>-<y>-objects.jpg
CR: Karina Linden
Oz Linden