**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
.HasProperty will check for a property existence but because the child types are returned as DynamicNull, you couldn't check for null equality.
Use DynamicNull's .IsNull (true) or .HasValue (false) or .Count() (0) or a typeof check
Expression Tree in DynamicQueryable explictly checks for this type and forces that portion of the predicate/expression tree to return true, bypassing the missing property
Handy when you are checking e.g. a boolean property in a .Where and that boolean doesn't exist on all nodes.
