Random fill for bucket replaced with Wang filling methods

[Bdtrotte]

To see the test working, load the tileset, select any tile, use the bucket tool, with random turned on. The map should be empty (doesn't yet take into account surrounding tiles not in the stamp).

Of course this code is quick and dirty, and will be drastically improved before actually becoming a part of the project. This is just a test to show the methods work, and for me to understand better how to implement the real thing, which I have a very good idea of how to do now :)

Also, if youre so inclined to build the set, this should work with any number of corners, doesn't yet work for edges as well though.