link Node Identity arch. spec. to OperationDocs Node Reg page
We define rules for naming the Node in the Architecture docs here: http://releases.dataone.org/online/api-documentation-v1.2.0/design/NodeIdentity.html
But the NodeRegistration page under MN_Checklist doesn't link out to it (This page is where the MN admin has to choose an ID to put into their Node document that will be submitted.