ENYO-2458: non-build services/providers may also need per-project UI

- ProjectConfig.js no longer contain any phonegap-related data
- project.json file format change (with backward compatibility)
- Each service/provider now provides its own default configuration
  (when Service#getDefaultProjectConfig is defined)

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