teiiddes-1633: Added check...  if tns in XSDFeature is null, then check the XSDComplexTypeDefinitionImpl instance.
Merge pull request #188 from tejones/teiiddes-1633

teiiddes-1633:
TEIIDDES-879: Surround loading of class with exception handling

* If the classloader fails to load the class, avoid letting an exception
  thrown so that the version can be found using the runtime client
  registry.

* This mitigates the possibility that users still have the original
  default Teiid driver instance.