grit and usenti updates

Git is now fully at 0.7. Or, rather, grit is at 0.7. As mentioned before, a name-change was in order and this has now taken place.

Other than that, there is little difference. Dovoto pointed to a bug in the tileset directory code which made me finally deal with the way directories were being handled. Unless told otherwise, the output goes into the current working directory. This is how it should be anyway. Non-binary changes are: updated documentation (for grit itself too) and a modified Makefile because it was out of date with the code itself (thanks Richard).

What's not been added are palette reduction and a more general tileset reducer. I have functions that can do these things (inside cldib), but applying them in the grit code base is … icky. There are so many potential problems with options here that I prefer to wait and add them later. Or maybe make separate tools for them.

I've also added the new Wingrit exporter to Usenti, which is now at v1.7.7.