ENYO-2571: Autoscroll enabled for the moved node after a DnD action

Related JIRA: https://enyojs.atlassian.net/browse/ENYO-2571

* As a node has been moved with a DnD action, it is now focused on the screen with an autoscroll.
* Autoscroll after refreshing the tree is now enabled: bug https://enyojs.atlassian.net/browse/ENYO-2575 fixed.

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