made a scrollpane replacement called scollPaneFancy

fixes issue where user mouseUp over an asset in a scrollpane while
scroll-dragging. both the asset->click and scrollPane->mouseUp fire at
the same time. scrollpanefancy sets mouseChildren=false while dragging.

also fixes issue when scrollpane is removed from the stage, it stops
listening for mouseevents from scrolldrag=true;
Exhibits can now "page" to next section