Adds 'Url', 'ItemType' and the Indexed property alias to IPublishedContent.

Changes Properties to ICollection instead of Collection for IPublishedContent.
Creates PublishedContentBase object which handles the Url and Indexed property on IPublishedContent automatically so implementors should use this base
class instead. Moves GetPropertyValue extensions to the Umbraco.Web project instead of the
Umbraco.Core project because this method needs to parse internal links if the value is a string. We require the UmbracoContext
to do this so they must exist in the Web project.

src/Umbraco.Web/Models/DynamicPublishedContent.cs

@@ -529,11 +529,26 @@ namespace Umbraco.Web.Models
 			get { return PublishedContent.Level; }
 		}
 
+		public string Url
+		{
+			get { return PublishedContent.Url; }
+		}
+
+		public PublishedItemType ItemType
+		{
+			get { return PublishedContent.ItemType; }
+		}
+
 		public IEnumerable<IPublishedContentProperty> Properties
 		{
 			get { return PublishedContent.Properties; }
 		}
 
+		public object this[string propertyAlias]
+		{
+			get { return PublishedContent[propertyAlias]; }
+		}
+
 		public DynamicPublishedContentList Children
 		{
 			get
@@ -739,7 +754,7 @@ namespace Umbraco.Web.Models
 			get { return PublishedContent.Level; }
 		}
 
-		System.Collections.ObjectModel.Collection<IPublishedContentProperty> IPublishedContent.Properties
+		ICollection<IPublishedContentProperty> IPublishedContent.Properties
 		{
 			get { return PublishedContent.Properties; }
 		}