**Breaking Change: DynamicNull.HasValue and DynamicNull.IsNull have been changed from properties to methods
Rename umbraco.MacroEngines.ExtensionMethods as umbraco.MacroEngines.PrivateExtensionMethods
Implement extension method invokes for DynamicNode
Moved Extension Method searching code to seperate static class
Moved all the defined extension methods for DynamicNode into the same ExtensionMethods.cs file
Changed the way that .ContainsAny within a where is evaluated to use the ExtensionMethodFinder class - should allow extra search methods to be defined