alt. PyPi project to minimize potential damage

To make sure that we don't create accidental damage and
disruption to our production users when introducing the
first BigJob/SAGA-Python release, I have created a new
PyPi project: saga-bigjob.

'pip install bigjob' will continue to install the old & working BigJob+Bliss
'pip install saga-bigjob' will install the saga-python version of BigJob

In case there is a problem with 'saga-bigjob', we can simply ask our users
to revert to 'bigjob'.