Clean up documentation of orchestration functions a bit.

Since caching is now a global behavior of functions, reformulate the
specific caching done by (some of) these functions to avoid confusion.

Remove some vague language about "the server doing whatever it wants",
and add **see also** links to all related functions.

Redmine #5232 - not closing the ticket, since it also asks for clarification
on what hubknowledge() exactly has access to, which needs investigation.