Add CamusHourlyCleanerHive

Like CamusHourlyCleaner (close to exact copy actually), but supports Hive style directory structure and actually works (incorporates https://github.com/linkedin/camus/pull/114).

It's not easy to override `outputDailyFormat`  and `outputMonthFormat` in all methods. Also: do not really want to diverge from upstream.

@ljank 
what about real `NULL`?