ming store similar to mongodb-based store
use config to import concrete class, we have to discuss how to address the different number of parameters given to our constructors.
tried to reorganize the worker... this is more a idea then a concrete solution, still not happy with it.
reorganization of worker, still not happy with it but a good starting point i guess.
as long as we do not have tests and tester is used, make the worker backend configurable.