Add tooltips to the navigator
Created by: Masboes
This was more tricky than I was expecting... MDL Tooltips require a unique id for each element that needs a tooltip, and since we have dynamic elements I had to come up with a unique id for each button in the navigator. Luckily each node already has a unique id, so I use those. Then it turned out that MDL doesn't like Angular dynamically updating its ids, so it needs an extra call. Anyway, long story short, we have tooltips on the buttons now. They are bound to the buttons themselves, so this should not give any problems in the new design of the website. Fixes #194 (closed)