Standalone data-checking scripts

[gold2718]

It would be helpful to be able to check data outside of running the compression scripts. Some script suggestions are:

• A script to compare a compressed file against the source files (currently being done by rcat_noresm.sh if the --compare spot or --compare full options are selected).
• A script to compare a directory of compressed and/or copied files against the checksum file created by rcat_noresm.sh
• A script to look for corrupted NetCDF files (history and restart)