Merge pull request #118 from Nurdoidz/master

Update all userstats classes
this implements #121 (online users counters per subverse)
updated removal of expired sessions
Temporary workaround for bug #122, needs proper exception handling.
this fixes #122 and #123
added top 7 subverses listing by number of online users to frontpage sidebar
this fixes #125 and #126
removed outline from voting arrows, thanks /u/Semperosa
minor corrections for better conformity with W3C markup validity