Upgrade plugin to 2.5.0 and new Apple UUID Policies

Hello,

I also use this plugin on Cordova 2.5.0 and I submitted a few updates in order to make this plugin working again with this version of Phonegap.

First, as stated [here](https://github.com/apache/cordova-ios/blob/master/guides/Cordova%20Plugin%20Upgrade%20Guide.md), I removed JSONKit references and used NSJSONSerialization.

Last, I removed the Unique Identifier reference, which not also is deprecated, but it would also made Apple to reject an application, as stated [here](http://tapbots.com/blog/news/udid-is-now-udidont). For iOS6 I used the new API proposed by Apple, for previous version I used [the OpenUDID project](https://github.com/ylechelle/OpenUDID), which had to be included to compile again this plugin.

Regards
Gian Luca Dalla Torre