Allow multiple connected maps

[otacke]

As an author, I want to be able to use a set of connected maps in order to enlarge the area that can be explored (similar to how Super Mario World uses tubes on the map).

Would at least involve:

• Using a list of maps (gamemapSteps) instead of just one
• Deciding what options should be choosable/reusable/overridable for each map individually (e.g. different background music for each map)
• Change logic to handle lists of maps (keep track of current map, change (re)storing the state, etc. )
• Add logic to jump between maps (display confirmation, visual transition, sound, ...)
• Change logic to handle individual options
• Amend special stages with a "teleport" option in editor
  • allows to choose a target map and a target stage from all the currently available maps/stages or to jump randomly
  • allows to optionally add a confirmation message (e.g. if returning to the previous map will not be possible)
  • allow to decide whether the stage can be used only once or repeatedly (default)
  • handles targets that were chosen but that then got deleted (set to random and display warning with list of targets)
• Add editor option for teleport sound