This implements the new annotation card truncation design
from https://trello.com/c/Jg0NWyF3/

The main consequence of the change is to make the annotation
cards more compact when truncation is enabled by:

 * Reducing the number of quote lines shown from 3 to 2

 * Showing the link to expand truncated quotes at the end
   of the second line of the quote, instead of on its own
   line

 * Moving the link to expand truncated annotation bodies
   outside of the annotation body and into a control
   inline with the tags list.

   This has been implemented by giving the <excerpt> control
   two modes, one that shows inline expand/collapse controls
   and a second that allows the containing directive to
   implement its own controls.