Define a schema that we can pass to jsonschema to validate against the
config a user has supplied. This will help catch a wide variety of common
errors that occur.
If the config does not pass schema validation then it raises an exception
and prints out human readable reasons.
Signed-off-by: Mazz Mosley <mazz@houseofmnowster.com>
When specifying the 'file' key to a value of it's own name, test
that this works and does not cause a false positive circular reference
error.
Signed-off-by: Mazz Mosley <mazz@houseofmnowster.com>