Expanded Python module for accessing LBS snapshots, and lbs-util.py.

Expanded Python module for accessing LBS snapshots, and lbs-util.py.

Expand the lbs Python module with code for reading from LBS archives.  This
includes decoding segments and parsing snapshot descriptors and metadata
logs.

Expand the lbs-util.py tool so that it has most of the functionality of
lbs-util (Perl implementation).  The Perl code should now be considered
deprecated, and will be removed at some point in the future.

The Python code still needs some cleaning up.