ENYO-2446: Drag'n'drop in file manager

ENYO-2446: Drag'n'drop in file manager

* use of HTML5 "draggable" attribute
* folder node expansion on hold over
* "package.js" update
* DnD cursor shows if drop target is valid or not

Checked on Windows 7 : Chrome, Chrome Canary
Note: autoscroll currently only works on Chrome, Chrome Canary, Opera

Ready to be reviewed

Enyo-DCO-1.1-Signed-off-by: Vincent HERILIER vincent.herilier@hp.com