tileset color mapping, modified background, about button

- removed redundant colors.txt from the tileset directories
- added missing color schemes for some tilesets
- added an xml mapping between tilesets and their default color schemes
- removed the install graphics button, users are now prompted upon
choosing an item

- the button to update save files shows properly again
- moved the dll files to the MasterworkDwarfFortress subdir
- added an about button to the menu