Ground work for Wino Calendar. (#475)

Wino Calendar abstractions.

Wino.Core/Integration/BaseCalendarIntegrator.cs

@@ -0,0 +1,9 @@
+using System.Threading.Tasks;
+
+namespace Wino.Core.Integration
+{
+    public abstract class BaseCalendarIntegrator<TNativeRequestType, TCalendarEventType>
+    {
+        public abstract Task<TCalendarEventType> CreateCalendarEventAsync(TNativeRequestType request);
+    }
+}