Added location of files, loc, to netcdf save

The location of the model output files used to run the numerical drifters for the simulation, loc, has been added to the function savetracks() for ease of reproducibiliity of results.
Added loc and git hash to particle track save

I can't figure out how to save a string to a netCDF4 variable, so I saved the empty variables 'loc' and 'git_hash' which in their 'long_name' metadata have their descriptions and values. loc has the location of the model output used to move drifters, and git_hash has the unique identifier for the commit version of the code used to do the tracking.