add: reimplemented cart table as a backbone view (increased flexibility,
move towards removing datatables as a dependency).

fix: better behavior for select boxes.  now close on button click and
focus doesn't change when check boxes are selected or deselected.

fix: previewed layers panel didn't remove tools dom elements on preview
tool close.

fix: removed some dependencies from common controls.

change: wms getmap no longer waits for wms describelayer info to begin
drawing.