TNL-56

STUD-2038

STUD-2048

Bug fix for dragging past last element in list.
STUD-879

Part of STUD-847.

Move overview-specific functions into overview.js.

There are possibly children nested below that.

Also includes RequireJS changes.

Fixes bugs:
STUD-755, STUD-152, STUD-700, STUD-699

Add CSS classes and fix drop destination bug.

Remove unused variables; some changes to match existing BDD spec for
drag/drop (expand-on-hover timeout and dropping with mouse outside of
element); bugfix for section expand; some code cleanup; update and
re-enable acceptance test.

Failed drags bring the element back to where it started; elements are
locked to the y-axis, states are represented as CSS classes for
styling, elements can be dragged across section/subsection borders,
and dragging to the top/bottom of a section Just Works.

Needs some styling love to give visual representation of where the
dragged element will drop, though.

TODO: It'd be good to have auto expand/collapse for subsections.