added playlist loader

registered appconfig as singleton
added config interfaces

Tv7Playlist.Core/IAppConfig.cs

@@ -0,0 +1,13 @@
+namespace Tv7Playlist.Core
+{
+    public interface IAppConfig
+    {
+        string TV7Url { get; set; }
+
+        SourceTypeEnum SourceType { get; set; }
+
+        string UdpxyUrl { get; set; }
+
+        string DownloadFileName { get; set; }
+    }
+}