[webui] merge the existant comment titles into the body

Fixes issue 546 as discussed in 2.5 meeting
[webui] slim down the display of comments

Now that we have no titles, we can display the whole thing a bit more compact
[webui] don't reuse project list between users

Wrote test case for issue #272 and noticed something:
hidden projects were in cache as the cache only validated there were no updates
to the list, not if things were removed. That was of course very naiv to write.