[#ENYO-1712] save selected phone gap build signing keys in project.json + fixes

* ENYO-1712: Preserve selected signing-key across Ares run (HEAD, enyojs/ENYO-1712, ENYO-1712)
* Merge branch 'master' of github.com:enyojs/ares-project into ENYO-1712
* ENYO-1712: Per-application key-signing choice (micro-tech/ENYO-1712)
* ENYO-1712: Fix services authentication state machine (really…)
* ENYO-1712: cleanup ServiceRegistry (indentation)
* ENYO-1712: cleanup ServiceRegistry
* ENYO-1712: Fix services authentication state machine
* ENYO-1712: tracing improvements
* ENYO-1712: fix ares.extend() usage instructions

Enyo-DCO-1.1-Signed-off-by: Francois-Xavier KOWALSKI <francois-xavier.kowalski@hp.com>