Stabilizing schema production unit testing

[wendellpiez]

PR #9 has more unit tests for schema production from Metaschema source.

However there is much more to do:

• Test and confirm unit testing works so far in this repo
• Add and test support for unit testing the XSD production
• Build out XSD unit tests to parallel the JSON tests so far
• Extend both testing suites

For this issue, it would be good to implement the first two tasks and plan the others.

Issue #18 provides the beginnings of a functional breakout of Metaschema showing where unit testing needs to be extended. This needs to be moved to documentation (readme files?) or a ticket.

[david-waltermire]

There is a good deal of work towards cleaning up the schema generation unit testing in #197.