Change 'move to top' to 'move above next meeting'

In practice, a 'move to top' button for deciding
what to work on next is annoying, since you
can't just think of what order you want to do
things in -- you have to continuously reorder
things after pressing the bump chevron.

So, let's try moving just above the Next Meeting
to see if it is a more natural behavior.
Version 0.8.3

This release finishes the potpourri of
features related directly to the task
list to be done before 1.0.

Since 0.8.2:
 * Tour: Include checklists, mileposts,
   update-status mindset

 * Mileposts can have custom colors

 * Revised the initial tasks created with a
   circle

 * Add and remove groups from members via the
   admin panel

 * Changed "What's Next" mindset behavior to
   bump task up to just above the Next Meeting