Backlog: Add grippy area to stories

Add 'something' to indicate that stories can be
moved, in preparation for working on a touch
interface.
Backlog: Only move from grippy area

To prepare for use on touch devices, only move
stories from a specific grippy handle, otherwise
it gets confused with scrolling.

Perhaps future work can allow us to use the entire
story area for drag and drop on touch devices,
but for now let's limit the area.
Backlog: Remove DDConstrained plugin

The DDConstrained plugin for the YUI drag and
drop module just messes things up on a small
viewport, like a phone, and I can't tell the
difference with it present or not in a large
viewport, so it's gone.
Backlog: Change the style of an active grippy

Change a little bit to help show that the
touchy things are working.