Use gloop_model to read and write .ply files.

Later, extend to read/write other formats.
Ignore editor backup files.
Improve mesh reading.
Include config header first.
Output ascii .ply files by default when writing to stdout.
Remove extra include of config header.
Refactor some geometry code into a utility library.
Begin work on a mesh info executable.
bunch of changes, particularly to geom code layout.