Ref T9304. This adds a "GuidanceEngine" which can generate "Guidance".

In practice, this lets third-party code (rSERVICES) remove and replace instructions in the UI, which is basically only usefulf or us to tell users to go read the documentation in the Phacility cluster.

The next diff tailors the help on the "Auth Providers" and "Create New User" pages to say "PHACILITY PHACILITY PHACILITY PHACILITY".

Browed to "Auth Providers" and "Create New User" on instanced and non-instanced installs, saw appropriate guidance.