Previously there was no differentiation between the same method at different
inheritance levels, therefore using the once_per_instance_decorator with super call would
prevent the super call from executing as they were considered the same
instance.
Add to/from_pod implementations to level, so that it may be serialized
properly. In order to make sure that serialization is a reversible
operation, ensure that the level value is numeric.
Tests now reside in the root of the repo, rather than in wa package.
This means they will no longer packaged and installed in user
deployments (they're only useful for developers).
