ENYO-3643: default phonegap version should be 3.1.0

* ENYO-3643: default phonegap version should be 3.1.0

Related JIRA: [https://enyojs.atlassian.net/browse/ENYO-3643](https://enyojs.atlassian.net/browse/ENYO-3643 "JIRA")

Enyo-DCO-1.1-Signed-off-by: Francois Connetable <francois.connetable@hp.com>