Some refactoring to decouple web based assemblies from Umbraco.Core and move whatever we can to Umbraco.Web where web based assemblies are used. Decouples System.Drawing entirely from Umbraco.Core and removes the Active Directory dependency from Umbraco.core.

src/Umbraco.Web/Security/IBackOfficeUserManagerMarker.cs

@@ -0,0 +1,15 @@
+using Microsoft.Owin;
+using Umbraco.Core.Models.Identity;
+
+namespace Umbraco.Web.Security
+{
+    /// <summary>
+    /// This interface is only here due to the fact that IOwinContext Get / Set only work in generics, if they worked
+    /// with regular 'object' then we wouldn't have to use this work around but because of that we have to use this
+    /// class to resolve the 'real' type of the registered user manager
+    /// </summary>
+    internal interface IBackOfficeUserManagerMarker
+    {
+        BackOfficeUserManager<BackOfficeIdentityUser> GetManager(IOwinContext owin);
+    }
+}