ENYO-2775: add file-system overlays & use it for Designer IFrame

Tested on OSX/ChromeCanary & OSX/Firefox with Node.js 0.10.16 & 0.8.25.
Crashes IE10...

* ENYO-2775: fix IE10 console error
* ENYO-2775: apaise jshint + sanitize logging
* ENYO-2775, ENYO-2901: re-enable file-system test suite
* ENYO-2775: drop deprecated `util.pump()`
* ENYO-2775, ENYO-1741: fix regression on error handling
* ENYO-2775: add file-system overlays & use it for Designer IFrame

Enyo-DCO-1.1-Signed-off-by: Francois-Xavier KOWALSKI <francois-xavier.kowalski@hp.com>