ENYO-2794: Generate Phonegap plugins in the "config.xml" from "project.json"

The feature is described in the readme section "Plugin integration" present in the last commit of this PR

Ready for review.
Tested on Chrome, FireFox, (Windows 7)
Enyo-DCO-1.1-Signed-off-by: Rafik Adiche mahmoud-rafik.adiche@hp.com