[primary/secondary] Replace fetch-from-master with fetch-from-domain-controller

Replacement of master/slave by primary/secondary:

1. The /host=* management resource’s ‘domain-controller’ attribute includes an ‘admin-only-policy’ field, one of whose legal values is ‘fetch-from-master’. A new legal value ‘fetch-from-domain-controller’ will be added. The wildfly-config.xsd will be revved and the ‘fetch-from-master’ value removed. However, the parser will accept ‘fetch-from-master’, setting ‘fetch-from-domain-controller’ instead. If a management client passes ‘fetch-from-master’ a deprecation notice will be logged at info (in the same log category as other such notices) and ‘fetch-from-domain-controller’ will be stored.