Ground work for Wino Calendar. (#475)

Wino Calendar abstractions.

Wino.Core.Domain/Entities/Mail/AccountSignature.cs

@@ -0,0 +1,17 @@
+using System;
+using SQLite;
+
+namespace Wino.Core.Domain.Entities.Mail
+{
+    public class AccountSignature
+    {
+        [PrimaryKey]
+        public Guid Id { get; set; }
+
+        public string Name { get; set; }
+
+        public string HtmlBody { get; set; }
+
+        public Guid MailAccountId { get; set; }
+    }
+}