Add missing cleanup_views functionality

[carlosduclos]

Original issue

satazor
See: http://docs.couchdb.org/en/1.6.1/maintenance/compaction.html#views-cleanup

[big-r81]

I'm closing this old ticket. If it's still a problem, please reopen or create a new ticket.

[nlfiedler]

I'm not sure if old views get removed automatically, so would this functionality still be needed?