MODE-2394: Updates to the Vdb Sequencer in line with Teiid Schema

* Updates the Vdb sequencer's cnd model and lexicon to reflect the schema
  included in the latest version of teiid.
My concern about this change is that while it is technically backward compatible (thanks to the `nt:unstructured` base type), the change is not *semantically* backward compatible. Existing repositories that have this content conforming to the old structure might have a `vdb:virtualDatabase` node with `vdb:sourceTranslator`, `vdb:sourceJndiName`, and `vdb:sourceName` properties, and as soon as the repository is upgraded to include this change in node type definitions, those existing properties essentially become second-class since they differ from the new structure with a single `vdb:sources` child node with multiple `vdb:source` children.

Basically, I'm not opposed to this change, but I want us to be very sure that this is the best/only way forward. IOW, I'd like more justification as to why these property definitions should be removed. Obviously with these changes, it is possible to have more than one `vdb:source` under a `vdb:virtualDatabase` node, and the old way is not capable of handling that. But can we still keep these property definitions (perhaps using a comment to say they are deprecated)?