First of all: sorry to all translators who started working on these new
strings!
We use CamelCase for our titles, and in particular "Plug-In" is
capitalized with 'I'.
Furthermore, let's use understandable titles like "Plug-In Example in C"
and not just "In C", because while the short title works OK in the menu,
it makes for very broken action names in non-contextual parts of the
software, such as the action search.
Note that we in fact have a concept of short label for actions since
commit 89772351c9. I added support for it to GEGL actions (cf. commit
6dc5f6792e), and to a few core actions (e.g. commit ea1205f094).
Unfortunately I don't think I added an API yet for short label in
plug-ins. Maybe I'll add it soon. But for now, if we have to have a
single label, it should be long, so that it works in every situation.
P.S.: not sure if it's useful to keep documentation strings just
repeating the title, but for now, let's leave them.