Add a test framework for types

[jackgr]

Currently, there's no quality assurance for types pushed to the registry, other than review by the registry owners. We've talked about putting a test framework in place, to check for things like:

• Schema file is present and well formed
• Schema file metadata is complete
• Type definition file is present and validates against the schema
• Referenced types/versions exist and are valid
• Referenced container images/tags exist and are publicly accessible
• Type expands and deploys successfully
• Type specific test suites supplied with the type pass

Tests should run when a type is created or updated. There needs to be a way to add type specific test suites to the type/version directory.