Added the Dune 2000 BLOXXMAS terrain tiles

Only the ones of interest. See http://d2kplus.com/wiki/index.php?title=Tile_Sets#Similarities. Part of the original 1.06 patch I promised to do for the christmas release. https://github.com/OpenRA/OpenRA/issues/4296#issuecomment-30542430 Better late then never I guess.