Fix various Model Extension issues with import/export DDL and vdb.xml formats

Current 11.1 Designer does not fully support import/export DDL and vdb.xml containing model extension properties, especially user's custom/logcal model extension definitions (*.mxd files)

Applicable actions
Model Explorer

• Select source model with table and procedure and apply custom MED via Modeling >> Manage Model Extension Definitions
  • set required properties
• In primary Model Editor tab for the source model
  • Select Export Teiid DDL and verify the DDL contains the OPTIONS() properties and the SET NAMESPACE statement
  • Select a table and click the generate data service (vdb.xml) toolbar button (bottom). Verify OPTIONS() and SET NAMESPACE are there
• Create a VDB containing the source model and open VDB Editor
  • Select Save As XML button and verify OPTIONS() and SET NAMESPACE are in the generated *.vdb.xml