FIX: Prevent "Add Page" button being stuck 'focussed'

Prevent the UI button getting stuck in its ‘focussed’ state, even after switching panels:

![screen shot 2013-12-16 at 14 41 17](https://f.cloud.github.com/assets/1655548/1755202/b268c712-6660-11e3-9feb-85a320dd6e7b.png)

I’m guessing this is because jQuery UI binds different events for anchors than buttons (namely `focus` and `blur` instead of `mousedown` and `mouseup`).