Use more generic way of saving world-specific data

This allows for saving of world-specific data in under a separate
structure under the the player scope.

In addition to the usual PlayerSave section, there is now:

PlayerSave_Altis
PlayerSave_Stratis

At restore time, the world specific data is merged with the generic data
before being re-applied.
Cleanup old way of doing world-specific position
Fix merged booboo
Merge remote-tracking branch 'upstream/Development_main' into Development_main