DAOImplementation: remove last traces

this design has been obsoleted.
AFSConfig: fix error in config-file determination

which prevented the system-wide config-file from being read at all.
AFSConfig.py: line shifting to not break logical units
setup.py: fix requires

We should not depend on a distinct db-technology, but SQLALchemy alone.
BosServerDAOTest: do not use BaseTest-setup

anymore. But use the @classmethod - method of unittests.
The former approach doesn't work nicely with async-execution.
BosServerDAOTest: fix usage of setUp.

It should really be setUpClass
async execution of low-level subprocesses

add the framework in BaseDAO, have a first implementation
in BosServerDAO and a first unit-test for one method in the
BosServerDAO, get_log