ENYO-2497: Undo the last DragNDrop move action

Related JIRA: https://enyojs.atlassian.net/browse/ENYO-2497

* As a node has been moved with a DnD action, it can be undone right after
* After any file action, the undo capability is canceled
* after any node moves, focus is now put on the moved node
* autoscroll after refreshing the tree is disabled due to bug: https://enyojs.atlassian.net/browse/ENYO-2575

Checked on Windows 7 : FF/Chrome/Chrome Canary/Opera/Safari/IE 9 & 10
Do not work on Safari: https://enyojs.atlassian.net/browse/ENYO-2554

Ready to be reviewed

Enyo-DCO-1.1-Signed-off-by: Vincent HERILIER vincent.herilier@hp.com