The enums exposed by the connector are not intended to be used by the
users of the library. The fact that the protocol, and other, modules used
it was in violation of how the library is intended to be used.
Adding an internal mapping into MaxScale also removes some of the
dependencies that the core has on the connector.
If the version if >= 10.2.3 recognized/builtin Json function should
be typed as QUERY_TYPE_READ while unrecognized ones should be typed
as QUERY_TYPE_READ | QUERY_TYPE_WRITE.
