**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
DynamicNodeWalker is our secret weapon in the fight against the Rebel XSLT Alliance
Navigate nodes by calling Up(), Down(), Next() and Previous() on them
Next(1) will jump two items along within the current list, whereas Next() will walk by one within the list
Previous(1) will move two items backwards within the current list
Up() is a special wrapper around .Parent which has an overload .Up(int) to replace @Model.Parent.Parent.Parent... [.Up(2)]
Down() will take you to the first Child item and is equivilent to .Children.First(), use .Down(1) to replace .Children.First().Children
If one of the NodeWalker functions fails to find a node at the requested position, it will return null
