ENYO-2740: Fixing problematic drag/drop - Regaining IE10 support

This commit fixes some of the problems seen during certain drag & drop
events. This also adds the proper "text" data type during ondragstart
events: e.dataTransfer.setData("text", data). This allows us to gain
drag/drop support in IE10.

Enyo-DCO-1.1-Signed-off-by: Jeremy Thomas <jeremy.thomas@lge.com>
Verifying beforeTarget exists before accessing props

Enyo-DCO-1.1-Signed-off-by: Jeremy Thomas <jeremy.thomas@lge.com>
re-merged with master
Hiding flightArea after animating to allow drag/drop in iframe
Merge pull request #555 from enyojs/ENYO-2740-jeremythomas

ENYO-2740: Fixing quirky drag/drop + IE10 Support