Upgrade citar-org-update-pre-suffix to iterate through all references in citation

[krisbalintona]

To resolve #607 and #606. The following pull request does the following:

1. Renames citar-org-update-pre-suffix to citar-org-update-prefix-suffix. I found the initial naming potentially misleading. This rename may increase the discoverability of the command.
2. Adds a helper function, citar-org--update-prefix-suffix.
3. (Unchanged) When on a reference, will prompt for a new prefix and suffix, with default values being their current values.
4. (New) When on a citation (but not a reference), will prompt for a new prefix and suffix for every reference in the citation at point from left to right.
5. (New) When on a reference and called with prefix arg, does the same as (4).
6. (New) There will always be only one space between citekey and citation suffix, unless there is no non-whitespace character in the suffix, in which case the suffix will be empty.

This new functionality uses purely the org-element API, meaning this should be a robust solution.

Additionally, I have manually tested the pull request through several edge cases, and have detected no bugs.

Finally, if this pull request goes through, I think it would be a good idea to (i) have citar-org-update-prefix-suffix be run after inserting a citation and (ii) have a customizable option to have toggle this behavior, potentially having it enabled by default.

[bdarcus]

Finally, if this pull request goes through, I think it would be a good idea to (i) have citar-org-update-prefix-suffix be run after inserting a citation and (ii) have a customizable option to have toggle this behavior, potentially having it enabled by default.

Yeah; I was wondering about that after testing it. ;-)

Perhaps on that you could also update the documentation?

https://github.com/emacs-citar/citar#org-cite-1

Thanks!