One global password for all CSE fields which can be edited

Issue Summary

This is such an awesome contrib, thank you!

I would love to have the option to have a single global password that works for all CSE fields.

Then, it would also be nice to be able to edit this single password periodically to help with our security. So then I give the master password to people who should have access to everything, and from time to time we can change that password and redistribute it.

It would be gravy to also have the option for individual cse passwords - this way if i have a user who should access one but not all, i give them that password instead of the global one.

Best,
-Sam