Add UWP support (#139)

* Add UWP project, and generate services boilerplate

* SqliteService implementation and sqlite-net-pcl update (#bug https://stackoverflow.com/questions/45418669/xamarin-forms-pcl-assemly-issue)

* Important services implementation

* Create a shared project to host images for UWP (to keep code project clean)

* Add extensions to image names referenced by the pcl project

* Add DismissModalToolBarItem to modal pages

* moving UWP folders inside src folder

* Add DeviceInfoService implementation

* Remove dependency on BouncyCastle, and calculate key derivation using native support

* changes requested by project maintener

* Fix HasCamera property

* DeviceActionService implementation

src/UWP/Services/HttpService.cs

@@ -0,0 +1,16 @@
+using Bit.App.Abstractions;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Bit.App;
+
+namespace Bit.UWP.Services
+{
+    public class HttpService : IHttpService
+    {
+        public ApiHttpClient ApiClient => new ApiHttpClient();
+        public IdentityHttpClient IdentityClient => new IdentityHttpClient();
+    }
+}