adding versioning to xml descriptors

[Marshall Schor]

There has been some discussion about adding something to the UIMA XML 
descriptors that
would indicate the "version" of the XML Descriptor - to allow for better 
future change
management.

Was this ever done?  Should this be a 2.1 item?  Probably would be 
"cleaner" to
introduce it as part of 2.x official releases...
-Marshall