add the possibility to collect data about the behavior of users
while looking at proposals and their comments, a prerequisite to fixing
hhucn/adhocracy#115
 - introduced a 'stats' controller to be used to collect various usage
   statistics to be used by this feature as well as future extensions
   (e.g. hhucn/adhocracy#167)
 - added an option 'adhocracy.monitor_comment_behavior' to control
   whether stats about comments should be collected
 - added background requests that are triggered iff the option is set
   and a user either scrolls or opens 2nd-level comments; for data to be
   collected, 'adhocracy.requestlog_active' must be set to True
add documentation to stats controller
insert space after if
remove return value from event handler
Merge pull request #265 from wawe/feature-comment-behavior-monitoring

Add the possibility to collect data about the behavior of users when viewing comments