Add openstreetmap.bzh

[brunob]

Project presentation is here http://tile.openstreetmap.bzh/ & tiles are visible here http://tile.openstreetmap.bzh/

http://tile.openstreetmap.bzh/br/{z}/{x}/{y}.png

Just have to find the max extent handled by the tileset, but i think it is "Bretagne" bounds.

Any thoughts about this ?