First skeleton for meta-data and production scripts

- extended prepareCrabJob.py
- created sample_utils module to handle datasets catalogs

Many pieces are still missing, in particular:
- the samples_utils are not fully implemented
- the only information stored in the LumiBlocks is the number of processed events.
  Information about sum of weight and PU distribution need to be added.
- standard microAOD sequences should be created

Extra:
- temporary fix to avoid flood of memory check messages raising logging threshold
- added configurable extra isolation to flashgg::Photon producer