allow file output without auxiliary files #260

A new argument was added to "OcgOperations" called "add_auxiliary_files".
These argument will create a directory with the output contents
if True or write the file directly if False.
removed constants.fill_value

This constant was causing issues with different data types. It is
better to delegate the handling of fill values to numpy to ensure
data types are compliant when writing to netCDF4-python.
always add calendar and units attribute to time dimension for netCDF output #167

Time attributes (units and calendar) are now added to time and bounds
dimensions.

Closes #167.