Make it clear whether a function is an Operation or just a Function

[josephjclark]

Adaptors export a bunch of functions to be used in job code.

Most of these functions are Opertions - outside of common, probably 99% of them are operations.

But some are just functions,

Operations and functions should be treated slightly differently by end users (see #428), so some kind of operation label/pill on the adaptor docs, or maybe a show operations only checkbox on the docs page, would be really helpful.

It would also be nice for users to see the docs and say "hey, what's this operation stuff all about?" and see a link to a really clear explanation.