* Refactor tests into "groups", each with its own filter (not/only/requires) to select which providers are appropriate.
* Test driver code is now a lot more simple and clear.
* Add support for not(), only(), and requires() as a way to select/reject providers for a test.
* Add docs explaining how to add tests
* Logging messages are much cleaner now, especially when tests are skipped.
* -start and -end now refer to test groups, not individual tests. Log messages list the group numbers clearly.
* Add stringer for Capabilities
* Change the order of the tests so that simple tests are first
* Removed knownFailures from providers.json
* fmtjson providers.json
Co-authored-by: Tom Limoncelli <tlimoncelli@stackoverflow.com>
