Fix #297, use TopicID for MsgID assignment

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[x] I reviewed the Contributing Guide.
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Describe the contribution Define CF MsgIDs based on TopicID

Fixes #297

Testing performed Build and run tests

Expected behavior changes None

System(s) tested on Debian

Additional context This supersedes the previous PR on this issue #298

Contributor Info - All information REQUIRED for consideration of pull request Joseph Hickey, Vantage Systems, Inc.

nasa / CF