Initial C# SDK structure and interfaces

Interfaces/IKeyringAPI.cs

@@ -0,0 +1,10 @@
+namespace Chtn.CSharpSDK.Interfaces
+{
+    public interface IKeyringAPI
+    {
+        void Set(string key, object value);
+        string Get(string key);
+        void Delete(string key);
+        void Flush();
+    }
+}