"New Tileset" dialog overhaul

[xan2622]

We could use the available palettes #4 (located in the project sub-folder) and display them in a drop down menu:

[xan2622]

So, the project would feature a folder containing all palettes, sorted "by mod" in sub-folders.

if the user pastes new custom palettes in new sub-folders, those would of course be displayed on the "New Tileset" dialog (instead of TD, here on the mockup image).