Begin validators
add threaded call to guestfs.mount_local_run()
improve threading use
Merge remote-tracking branch 'origin/master' into juphoff/validators
simplified calls
drive functionality from command-line arguments
Validator development.

- Split libguestfs initialization apart from FUSE mounting.
- Add docstrings.
- Ensure FUSE filesystem is unmounted before exit (to prevent
  'Transport endpoint is not connected' errors).
Turn off tracing by default.
Perform search for module.
Add sleep (racy) to work around thread deadlocking in Python.
Change from threading to multiprocessing library to avoid Python
thread deadlocking.
Add info for validators.
Add verbose output and proper clean-up.
- Handle verbose and quiet output requests.
- Handle non-image (basic filesystem access) case.
Add direct API (non-FUSE) check for module.
Handle image-based usage without FUSE.
Only look for a mount point argument when it's useful.