JPSSnagg

- Change tests for compression and layout changes to grep output for specific words such as COMPRESSION or CHUNKED in outup to avoid differences between HDF5 version for the VALUE output of a Fill_Value setting.
- Add code to set maximum number of granule information pointers to value of environment variable "MAX_GRANULES_NAGG" if it exists instead of the defined limit NAGG_Granule_info_max, to allow users to temporarily raise the number of granules that can be processed by nagg.
 - If the number of granules in a product group is not the same as the value of the AggregateNumberGranules attribute of the Aggr dataset, use the actual number and issue a warning to stderr.