Rename algorithms #257

I've renamed algorithms ``PA``, ``PA1``, ``PA2``, ``CW``, ``AROW``, ``NHERD`` of classifier and ``PA`` of regression. Naming convention is discussed in issue #257. I've also added algorithm names for configuration in ``classifier_factory`` and ``regression_factory``, where old names are not removed for compatibility.

Other naming violations on abbreviation, e.g. zookeeper as zk (including ``zk``, ``cached_zk``, etc.), have not been fixed yet, because they would influence on much wider codes.