Allow resolving JSONSchemas with specific tags

The /schemas endpoint is not correctly returning schemas when the version tag is provided (e.g. baseclasses.wet_chemical_deposition.spin_coating.SpinCoating@d4c253b938af0450e70345fa5b4399f4c6552d35).

This should be fixed by first using the class path to resolve the class, and them checking whether the tags match. If they match return the class, if not, raise a 404. Later down the line we should instead have the schemas in MongoDB.