OASIS/SRU: Multiple Query Types -- draft message

Draft message.

This one is straighforward, so if I don't hear from anyone in the next
couple hours I'll post it.

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There is a suggestion to support multiple query types. (As Z39.50 does, but
SRU does not.) Parameterized Query is an example of a new query type that
does is not easily modelled as a CQL query. And there are possibly other
query types that we may want to model differently than CQL.