#401 Add new earthwall graphics

[Saiapatsu]

Replaces all bwall, earthwall and stoneblock graphics in arch/wall/bwall, adds three (loosely conformant...) LICENSE files and moves the previous graphics to the clsc tileset.
Images were compressed/encoded with imagemagick.
I have variants of bwall_w_1.base.117 and bwall_w_0.base.117 without the rubble (i.e. like a one-tile gap in the wall), but there appears to be no arch or need for them.

The patch file has been confirmed to work with git apply patch

[Nicolas Weeger]

Applied as 50df56b8c1cf70014341e34929e133d340174295, thanks :)