New workflow for users to update the global config file

[alisnwu]

Problem

Need a better workflow for users to know how to update the global config file easily.

Proposed solution

Current instructions are in documentation for diffpy.utils so maybe we can include some message that gives instructions or points to the documentation

[sbillinge]

I agree. I think it is ok if it is in the docs, and a short link to that where it is needed.