Clarify open functions, APIs

[bdarcus]

As followup to #509 discussion, we need to settle what we want to do with these functions longer term:

1. citar-open
2. citar-open-library-file
3. citar-open-link
4. etc

Specifically, there are two changes that should impact our answers here:

1. embark-act-all
2. use of cosult-multi in citar-open in particular (see Add groups to citar-open functions #491)

No rush on this; I just put it here because we do need to settle the plan. I also need to think about it more.

I will say my preference is to keep the code as simple as possible to maintain and build on, and that it's currently too complicated in places in my view.

cc @roshanshariff @localauthor

[bdarcus]

Closed via #634