Create ansible role to create/update a section in /etc/cyhy/cyhy.conf for every mongo user

[dav3r]

From #161 (comment):
Create a separate Ansible role that creates a cyhy.conf with credentials for each and every user in mongo_users.other_users. That way there will be a conf file section available for any Mongo user that anyone wants to use. This will cause some heartburn, though, since the credential sections will have to be named using the MongoDB username. (Right now they are named willy-nilly.) That will necessitate some changes elsewhere in the code where named sections from cyhy.conf are explicitly referenced.