Move base into ownmacro/slot, make other urls relative

There is now only one absolute url left. Unfortunately base tags
cannot take relative paths. We can hack this using JS.
Make all paths relative, drop base tag

For this demo, it is okay that we operate <base/>less. The slot is still
there and will be filled up remix.
Clean up our settings file a bit.
delete note configuration in js
Merge pull request #15 from oerpub/oerpub-ticket372-pull2

Remove absolute paths from the demo
Consult configuration, skip table config if asked to.
Disable table editor in title editor
Merge remote-tracking branch 'origin/oerpub-ticket432-pull' into undo-plugin