Update plugin.xml

[mm0000]

• File was empty, made it match the tutorial in the book.
• Added a fix for Cordova IOS builds outside of Xcode e.g. Intel's XDK. These tools do not supply the option to specify which frameworks should be added in the build proces. By adding the reference to the CoreTelephony.framework in the config the build process itself will add the framework when trying to build the app.