add more filter options to the ui; not implemented yet
Merge branch 'master' into feature-filter-more
implement order by due and title
add sort indicators

best practices suggest that up arrow should mean ascending,
although between the confusion of whether the arrow is an indicator or
a toggle button, and the natural order of things, means it's useless
anyway, and people just look at the result of the ordered list.
extract a directive for a button to order;

use it and add I and U order too
fix open of by due date
implement select behaviour for by due date
filter by due date selector