Remove dependency node

[jiricekcz]

Add methods for removing dependency node, so that we can removed created objects from the dependency tree.

[jiricekcz]

Also should be combined with a geometry object to create a method, that removes the object both from the plane and the dependency graph.

[jiricekcz]

Functions, that don't do both could also be marked as internal - not to show up in the documentation. They will still show up in intellisense, so this should be considered.