* Added support for asking if a given node type can have children or grandchildren and what types of nodes can be it's parent or child
* Removed canHaveChildren methods from leaf and branch nodes and converted use of them to depend on factory to read static rules from constructor lookup by type
Change-Id: I9769f95647066576416bacb791c4b68dd0285b35
Neither of these nodes have elements around them, so they must override the default behavior of ve.dm.Node
Change-Id: I19c02c210bfc04b6e2ee1a37b8890e84a236eee3