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.
If I read this line correctly, the return value of getListOfActiveJobs has changed. This is not good (i.e. breaking backward compatibility)! In addition, it is not documented and not immediately clear what the return type is and which piece of information is where.

Could you please explain why changing the return type is absolutely needed? Are there alternatives?