MC12b flag

Adding MC production flag (MC12a, MC12b) for the production-specific settings in SUSYTools. The `m_mcProd` flag is added as a member to the SusyD3PDAna class. The flag is controlled by the user with the command line argument to NtMaker:
`NtMaker -p mc12a ...`

The presence of the argument is not explicitly enforced by the NtMaker main() function, so it is not needed when processing data. However, if the sample is treated as MC (as always, determined dynamically from the sample name), and this flag is *not* set, then SusyD3PDAna::Begin will spit an error and abort.

The automatic determination of this flag was added to the grid submission script. A new function parses the dataset name, extracting the reconstruction tag, and returns either mc12a or mc12b by comparing the tag to the known mc12b tag (r4485):
```python
mc12bTag = 4485
if recoTagNum < mc12bTag:
    return 'mc12a'
else:
    return 'mc12b'
```

The mc12b reco tag was taken from this page:
https://twiki.cern.ch/twiki/bin/viewauth/AtlasProtected/AtlasProductionGroupMC12b

This fixes issue #4