partial update to show when a thread has unread comments (for #200)

I want to wait to see what happens with main.js after a few merges re #212, so this only gets it part of the way there. 

The news controller contains a new function which adds the date and id of the user of the latest comment, which is then added as data attributes to the comment link item in the index template. Not done is the part that keeps track of changes to that and does something to indicate new comments. 

This also includes Google's sessionstorage, but isn't implemented yet, and that might not be the optimal solution, so i'm leaving it undone for now.