Working hover to show ached note

Added new tooltip_note CSS class
hovering over the triangle icon shows the public notes
ALso, triangle ONLY shown on main page when PUBLIC notes are available, and those are they only types shown in the tooltip.  Can still see admin/recurring notes when window is opened.
TO DO:
Hide admin notes
hide duplicate notes
Profiled to speed up assignment.py: mainly by speeding up list_active_rads by caching results instead of going to DB each time
Option to not show a new input form -- useful in edit cell.py for example.
Slight optimization for stats - streamline Isodate __cmp__ function a bit.
Merge branch 'refs/heads/master' into notes_cleanup
todo: added descriptions for new features, day off scheduling alto
TODO changes only