lml/ost#346: Make feedback penalty configurable.

- Add feedback penalty field to the settings store.
- Add feedback penalty to show and edit views.
- Add JS to show / hide penalty based on feedback required.
- Add help file for @kjdav with some help text.
- Ensure score detail page does not need any updates.
Ha ha ha - yeah.  Good thing is, code like this would soon be history :)