Move map related settings from [Startup] to a new [Map] section in OpenSim.ini

Existing map settings in [Startup] will continue to work, and if present will override anything in [Map]
However, the proper place for such settings would now be [Map]
This is to reduce the use of [Startup] as a bag for non-generic settings which should really go in sections, in common with other settings.
This commit also extends Diva's previous work to allow a default setting to be given when looking at multiple sections for settings.