Add request to change the order of a child node (or nodes) relative to the other children

The current DNA Graph model does support ordered children, and while rename can be used to change the order of same-name-siblings, there currently is no way to change the order of the child nodes. This is required to fully implement the JCR API.

JCR handles this functionality by provided a method that essentially changes the position of a single child node. The "Node.orderBefore(String childNameToBeMoved, String nameOfChildAtPosition)" can be used by calling on the parent node and supplying the name (with SNS index if needed) of the child to be moved and the name of the child before which the other child is to be moved.

This same model can be used for the graph request. It also would allow adding in the future another optional request that would contain multiple reorders, and that could be implemented in RequestProcessor to break into multiple ReorderChildRequest instances.

The existing (writable) connectors will all be affected, since this will be a new mandatory request.