Logging, autodetection, and some metafiles.

See each comment's long description for the individual details - the callouts here are autodetection of Pebble ID, logging based on the Python logging module, and a little work to make libpebble easier to use as a submodule.

The logging change is probably the most controversial - I needed them to debug issues with my Air's bluetooth (and my attempts to repack a tweaked watchface :) and thought it might be a good start / useful for others.