Dataset classloader not updated in the Explore cache when dataset types are updated

When we want to update a dataset module, because the jars of the types it encompasses have changed, we delete the modules, and then redeploy the dataset jars. Yet, in the Explore module, the DatasetAccessor class caches classloaders for all the dataset instances it has loaded so far, and the classloaders for the updated dataset instances will not be updated - creating inconsistencies when running Hive queries.