[Piglit] Rename generated tests

[Dylan Baker]

Patches 1-6 rename the directories used by generated tests to be
consistant with the names used by the static tests in the tests/ folder.
The difference is that in tests/ all extension names are lowered, but in
generated_tests/ they use mixed caps keeping consistancy with the spec
names.

Patch 7 changes some tests that have numbered names to have useful
consistant names. This information is already available and is rather
trivial, and should actually make the generator a little faster.