added template script for counties subsetting

The script subsets a group of CMIP5 datasets by county boundaries.
minor
i-191: output netCDF format broken for MFDataset to single netCDF

MFDataset could not properly be written to netCDF due to the format
coming back as a list of strings. The condition is now caught and the
first format is chosen.
Merge branch 'i-191-mfdataset'
i193: remove sample size as default output for calculations

A new parameter called calc_sample_size was added to OcgOperations.
The default (False) means sample sizes will not be computed for
calculations.
Merge branch 'master' into dev