Add collapsible navbar

[ekstroem]

Potential enhancement: collapsible navbar.

Potential problems:

1. included a link to jquery
2. The default css code for the navbar (in particular the logo) looks slightly strange since the navbar is flushed down relative to the logo. It may need some tweaks in the main css file
3. I haven't cleaned up elements in the master css tile that aren't needed

See a running example at www.sandsynligvis.dk [that is tweaked slightly relative to this]

This should include request #40