* PhoneDialer.cs: Add phone dialing class to Android

* IDialer.cs: Call interface

* PhoneDialer.cs: Add dialer class for iOS

* Axai.sln:
* Axai.csproj:
* Axai.iOS.csproj:
* packages.config:
* Axai.Android.csproj: 

* AndroidManifest.xml: Add permision to call and Internet usage

* ContactForm.xaml: add call button and number

* ContactForm.xaml.cs: add call method

* packages.config: Update newtonsoft.json package