Adopt directory structure from UQM 0.7.0.

Unfortunately this answer from the FAQ is outdated:

http://wiki.uqm.stack.nl/The_Ur-Quan_Masters_Technical_FAQ

It really seems to be for 0.4.0, so we needed to adopt some paths.
In addition, this also adds the "spin" directory from the 3do version which is
supported by the current SVN trunk of UQM, so we are forwards-compatible :-)

Signed-off-by: aszlig <aszlig@redmoonstudios.org>