JPSSnagg

start_write(), write_granules(), end_write() will write 1 to the number of granules in a pair (sensor data and geolocation) of input files to a pair of output files.  
Writing granules starting from a granule number > 0 causes hdf5 errors for now and will need to be addressed tomorrow.

A loop to write the number of granules specified by -n on the command line was added to nagg_main.c.  specifying more files that are in the input file will cause a segmentation fault currently which should also be addressed.

Tested on jam and koala.