changed placement of collapse button divs so they are put into center
'map' pane and positioning is done only via CSS. There is no longer a
need to maintain the original width/height of the pane.

allow for a splitter to be used with panel. With the change to css
positioning, button stays at edge of pane while resizing.

added support for an optional top pane.

moved the right/bottom/top panes to config/viewer to demonstrate how
that is done.