Configuration Panel

Provide Panel for stuff like
  - [ ] Settings field for Webmaster tools Verification - [Issue #271](https://github.com/screenconcept/kuhsaft/issues/271)
  - [ ] default page title/keywords/description
  - [ ] favicon
  - [ ] google analytics key
  - [ ] typekit id
  - [ ] 404 page (selectable from page tree)


- [ ] Allow adding custom settings via key/value
- [ ] Provide clear API for using settings in host application