... from menus.
The script-fu version is still available through pdb (for scripts) and
even in the action search. But in menus, only the new Python version
will be shown. Also update the description and name of the old version
to make clear it is deprecated in favor of the new plug-in.
Finally rename the new version to simply "plug-in-spyrogimp" (dropping
the "-plus" part as we should consider it as a replacement rather than
as another plug-in, which the "plus" would imply). Anyway the old one
was called "script-fu-spyrogimp", so there is no name clash.

While at it, do some trailing whitespace cleaning in the new plug-in.

(cherry picked from commit 8729f9a6)