Tweak visual appearance

- Use color NRW logo
- Map highlighting using NRW colors
- Specify color for visited links

See https://wiki1.hbz-nrw.de/display/SEM/NWBib-Treffen+10.9.2014

@acka47 assigning to you as we don't have a separate issue. If you +1 here, I will merge and deploy to production.

Deployed to staging: http://test.lobid.org/nwbib