upgraded all plugins to work with the new post-pro.

This is done "cheaply" for now, by only using old-style list-based datasets.
Taking advantage of the abstraction (so that we can use the plugins on all
datasets) will require more work. The hooks for transparent data translation
are in place, but the actual translation has not been implemented yet.

moving to new post-processing database

                    *** WARNING ***

do not upgrade if you need plugins or adaptive views: these have not
been ported (yet) to the new database

                    *** WARNING ***

new plugin to extract the geometry edges