Adding MC production flag (MC12a, MC12b)

`m_mcProd` member is added to SusyD3PDAna for specifying the MC production
campaign of an MC sample. This is necessary for the initialization of SUSYTools
because it uses different settings for mc12a and mc12b.

The flag is controlled by the user with the command line argument to NtMaker:
```NtMaker -p mc12a ...```

If a sample is recognized as MC (does not have 'data' in the sample name)
and the MC production flag is *not* set, an error message is printed and the
code aborts in SusyD3PDAna::Begin.
Added mc prod determination to submit script.

A new function, get_mc_prod, parses the dataset name
for all MC samples and uses the reconstruction tag (e.g. r4485)
to flag the sample as mc12a or mc12b. It then applies the appropriate
argument to the command which is run on the grid.
fixed mc12bTag usage
update doc string for get_mc_prod
Merge pull request #6 from gerbaudo/mc12b-flag

MC12b flag