Added platform themes to sencha touch

Added the platform specific themes provided by Sencha Touch 2 to the PropertyCross app.

In order to do this, Sencha Touch 2 was updated from version 2.2.0 to version 2.3.1.  These themes are discussed on the [Sencha Touch 2 blog](http://www.sencha.com/blog/announcing-sencha-touch-2-3-html5-for-ios7-touch-grid-cordova-support-more/).
> Announcing Sencha Touch 2.3 - Touch Grid, Cordova Support, and New Themes