Change navigation bar for mobile website

[stefan-mueller]

As discussed with @ciflikli a couple of days ago, the navigation bar for the mobile version of the website currently does not look very nice, and we'd prefer a hoverable and responsive navigation bar (comparable to this example).

[kbenoit]

Looks ok on an ipad in landscape mode, but in portrait on a phone or tablet, it’s a drop down box. Many other portrait mobile websites use the small sway RE box with the three lines. I don’t think the current version is that bad. Anyway I’d say this is not a high priority.