AfterContent tabs are now stateful

After reloading a page, the recently selected tab in the 'aftercontent'
section remains selected. This is still not stable across pages, but
resembles more the expected behaviour on page reload, e.g. in order to see
whether someone has responded to one's shout.

Change-Id: Ib6021cfac7b23209b3b78d3f7c2c5cdf8907a7e4
Merge "AfterContent tabs are now stateful"