The files in this directory are:
   - production plugins
   - demo plugins
   - initialization scripts for ScriptFu

Don't put test plugins in this directory, but in subdirectory test.

Production plugins:
  - installed in a release.
  - appear in diverse menus, not just Filters.
  - should be marked for translation, and not in potfiles.skip

Demo plugins:
  - installed in a release (with goat exercise plugins)
  - appear in Filters>Development>Demos
  - FUTURE: marked for translation, and not in potfiles.skip

Initialization scripts
  - loaded by the TinyScheme interpreter
  - have suffix .init or .scm
  - are not plugins
FUTURE:
The initialization scripts should all have suffix .scm
(like the rest of the Scheme world.)
They should be in a separate directory
so advanced users can load library scripts.

The files script-fu-util.scm and script-fu-util-setpt.scm
are also initialization scripts but loaded differently from .init files.
FUTURE: unify loading of initialization scripts.