Implementation of array jobs

Small improvement over merge request #12 

Finally enable submitting array jobs via the ```submitArrayJob``` method of ```Batchelor```. This method calls the ```submitJob``` function of the underlying implementation, for the moment this can be done at E18, GridKA and Lxplus. ```getListOfActiveJobs``` was adjusted to return a list of tuples containing the job and task IDs (and the status), ```submitJob``` continues to return only the job ID.

Possible issues:
* Tasks at Lxplus mean something entirely different from what they mean at E18 or GridKA.
Another thing which just occurred to me: except gridka, lxplus and e18, the other getListOfActiveJobs functions have not changed, so the return value is now dependent on the batch system one is working with -> very bad.