Adds ellipsis to unit list headers
Adds ellipsis to unit list headers

The unit list headers could overflow pushing the chevron onto the next line
when the unit status name is too long. This branch maintains the unit number
and chevron in their appropriate places while limiting the length of the
unit type when closed.

R=gary.poster
CC=
https://codereview.appspot.com/32260044

mitechie/juju-gui,mitechie/juju-gui,jrwren/juju-gui,bac/juju-gui,jrwren/juju-gui,bac/juju-gui,bac/juju-gui,bac/juju-gui,mitechie/juju-gui,jrwren/juju-gui,mitechie/juju-gui,jrwren/juju-gui