Add Cordova 2.5.0, add Facebook plugin

Added Cordova 2.5.0 for backwards compatibility with the PhoneGap
Facebook Connect plugin
(https://github.com/phonegap/phonegap-facebook-plugin).
Add Facebook plugin (JS) to index.html
Add Facebook plugin

Added fully functioning Facebook plugin to main.js, still without using
Parse. It works through the Cordova Facebook plugin.