CORE-4304 Updated data error messages.

Updated the getErrorMessage methods in the services.errors Category classes to return SafeHtml, due to the ServiceError interface update.
Added appropriate path getters to all ErrorDiskResource interfaces that were missing them.
Updated all services.errors Category classes to parse display labels from any paths contained in their errors, before generating error messages with them.
Added null checks to DiskResourceUtil name-from-path parsing methods.
Updated GetDiskResourceDetailsCallback::onFailure to attempt to parse error JSON.