adding mocks archiving scripts

[shadaba]

This PR is to add the script used to archive the mocks.
You can find the documentation about the FIrstGenMocks archive on following wiki:
https://desi.lbl.gov/trac/wiki/CosmoSimsWG/FirstGenerationMocks#ArchivingFirstGenMocks

There is also a notebook ArchiveFirstGenMocks.ipynb which walks you through how these scripts were ran.
Please be careful and do not run this again on NERSC as this might initiate backup once again.
The notebook also give examples of how to search for file or directory.

[shadaba]

@weaverba137 This pull request is to add the mocks script. Please take a look and let me know if things needs to change.

[weaverba137]

@shadaba, I suggest rearranging things as follows:

1. Move the *.py files to the bin directory.
2. Move the *.ipynb notebook to the etc directory.

This will allow the Python scripts to be available after module load desiBackup.