Merge pull request #178 from enyojs/ENYO-1712

[#ENYO-1712] refactor PhoneGap build to enable signing keys
Merge branch 'master' of github.com:enyojs/ares-project into ENYO-1712
ENYO-1712: Preserve selected signing-key across Ares run

Enyo-DCO-1.1-Signed-off-by: Francois-Xavier KOWALSKI <francois-xavier.kowalski@hp.com>