harvestingkit: first implementation of harvestingkit_cli

* harvestingkit_cli.py: Implements a console interface that let's
  the user execute the harvesting scripts from one central place.
  Also provides a way to change the user credentials for those
  scripts.

* configparser.py: Since the user credentials for the harvesting
  moved to user_config.cfg, configparser provides a way to load
  those credentials.

* scoap3utils.py: changed the logger in create_logger to log to
  the console as well as to the file.

* setup.py: Copies the user_config.cfg file to one of the places
  specified in setup.py.

* adds MissingTagException and a brief description to _get_text_from
  _journal_item

* some general cleanup

Signed-off-by: Martin Vesper <martin.vesper@cern.ch>
Should we finally just rename `CFG_SCOAP3DTDS_PATH` to `CFG_DTDS_PATH` or do this variable have to be named this way?