Update file header for bridgedb.Main module.
Move config functionality to new bridgedb.configure module.

 * MOVE bridgedb.persistent.Conf → bridgedb.configure.Conf.
 * MOVE bridgedb.Main.loadConfig → bridgedb.configure.loadConfig.
 * CHANGE imports in bridgedb.Main and bridgedb.persistent to use class
   and function in bridgedb.configure.
 * CHANGE Sphinx documentation to point to new locations.
Add unittests for bridgedb.configure module.