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.
I trust that this change makes something sensible. However, it would be nice to have some comments to what all this list stuff is actually doing so one can follow more easily. Maybe add an example output of the qstat commands?