Initial submission of configuration file changes.

 * MANIFEST.in: Add new config directory.
 * config/config.yaml: New, contains specs previously found in
   pyrseas/augment/*.py files.
 * docs/{cmdargs, config, index}.rst: Document configuration files and
   command-line options.
 * pyrseas/augment/{audit, column, function, table, trigger}.py: Move
   configuration specs out to config/config.yaml. Add 'config' args to
   constructors.
 * pyrseas/augmentdb.py (cfg_section): New helper function.
   (AugmentDatabase.AugDict.__init__): Add config arg and use it to
   use it to initialize various dictionaries.
   (AugmentDatabase.from_augmap): Pass config to AugDicts constructor.
 * pyrseas/cmdargs.py (cmd_parser): Add --config option.  Reorg host,
   port and username options so that they display any specified
   defaults.
 * pyrseas/config.py: New module to read and merge the configuration
   files.
 * pyrseas/database.py (Database.__init__): Add config parameter and
   use it to set attribute.
 * pyrseas/{dbaugment, dbtoyaml, testutils.py, yamltodb}.py:
   Instantiate a Config object and pass it to cmd_parser and to
   Database or AugmentDatabase constructor.
 * setup.py: Add data_files for config.yaml and dbaugment as a
   console_script.
 * tests/augment/test_audit.py: Change indentation due to config.yaml.
 * tests/test_config.py: New minimal test.