Vdb sequencer

Enables complete top-down export of modeshape vdb nodes, including DDL and Teiid SQL.
Do you think the relational model objects found in the `org.komodo.relational` plugin should be used when implementing this class? The objects in that plugin hide the JCR implementation. I find myself thinking that the logic that converts JCR nodes into Komodo-usable Java objects is sometimes being duplicated. I realize those objects in the relational plugin weren't written yet when you wrote this so this is a kind of after that fact comment.