Support running Moore in Ganga
Refactors some PyConf/Moore configuration logic to enable running Moore in Ganga. This allows Moore to be easily run on the Grid over a large number of files.
Adds a few tests which check that:
- Moore can run when input data is specified in a Ganga-like way (#93 (closed))
- Moore can run when no input data is specified (#95 (closed))
- Except for when the MDF IO service is used, which requires a non-empty input file list
- PyConf fails if some 'input metadata' properties is not set, like DB tags and input format
The last point is a bit gross because the PyConf example must now set these options, even though it runs over no input. On balance I think this is OK because PyConf is for LHCb, not Gaudi, and we always run our applications over data except when debugging. Still, other suggestions are welcome.
Closes #93 (closed) and #95 (closed).