ENYO-2458: update default phonegap version to 2.5.0

This is the minimum version acceptable to the Apple App-Store.
ENYO-2458: re-enable phonegap config.xml generation

Move the file generation from the generic ConfigProperties into the
phonegap/Build.js

Current status was to not provide config.xml at all:  every mandatory
parameters are provided in the query string.

While Ok for many apps, it does not fit those that want to load plugins,
such as the ChildBrowser needed for the OAuth dance.

Enyo-DCO-1.1-Signed-off-by: Francois-Xavier KOWALSKI <francois-xavier.kowalski@hp.com>
ENYO-2458: make project.json visible in HermesFileTree (FIXME)

- to be reverted after demo

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