[#7644] ticket:658 Script to generate a lot of new projects
[#7644] ticket:658 Pre-populate roles cache to reduce # of mongo queries

Also fix users_with_named_role so that it would actually use cache.

Template for `/nf/new_projects/` displays admins for each project (and
there can be a lot of projects) and it generates a lot of mongo queries to
lookup user roles. Pre-populating the cache once helps to reduce query
count more than twice, and improves overall page rendering time.