Add some Javadoc
Improve Category administration
Move the category rendering to JSP as well

It's a bit hacky right now, switching between JSP scriplets and EL, but
it seems to work well.
Add button to add an RSS/ATOM feed
Fix regression that unread articles were not displayed in the category tree
Translate the 'no unread' text
Don't display a blue box around active entries, just the left border

Also increase vertical spacing a bit
Allow entries to be clicked to jump to their position
Fix regression that scrolling up did no longer update the active entry
Fix regression that texts could overflow the entry boxes again