Revert "Merge branch 'pr-384' into 2.0.x"

This reverts commit ff6607aacaf4870e898e89a19398bdd174138a43, reversing
changes made to ea4e7af7888f8dda01f8ffbec645cdd6e64ec712.
AUI-1114 Treeview shows hit-place for dropping when dropping is forbidden
AUI-1114 Update demo - add tree with undraggable elements
AUI-1114 Check boolean first than dom operations for performance
AUI-1114 Source formatting
AUI-1114 Source formatting