remove basetile

basetile is similar to "Pos 0 0 FULL"
if there is no rule for pos 0 0 the default rule "Pos 0 0 FULL" is added
so we dont need basetile
also basetile is not as good as "Pos 0 0 FULL" because it does not reset flags like rotation of tiles
you can still write basetile but it will be ignored