ENYO-3354: Add a function to "Phonegap.ProjectProperties.Picker" to define a "None" element.

Link to the JIRA ticket: https://enyojs.atlassian.net/browse/ENYO-3354

Ready for review.

Tested on Chrome(Windows 7)
Enyo-DCO-1.1-Signed-off-by: Rafik Adiche mahmoud-rafik.adiche@hp.com