Support RPG Maker map files

This would be mainly to help people move away from RPG Maker, that have already done a lot of work on their maps. But if combined with saving to RPG Maker map format, it could also simply offer people an alternative for the built-in map editor.

Of course, there are many versions of RPG Maker and generally no documentation about their map formats is provided. But there's bound to be resources online written by people who have already tried to reverse-engineer the map format.

• RPG Maker 2000/2003 - Forum thread discussing the format, EasyRPG lmu docs, OGA forum thread
• RPG Maker XP
• RPG Maker VX
• RPG Maker VX Ace (requested on the Tiled forum)
• RPG Maker MV