Ability to set view automated index updates updateInterval per design document

A customer would like to set updateInterval at the design document level, this would override the system wide setting for updateInterval.

The documentation doesn't make it clear which settings (updateInterval, updateMinChanges, replicaUpdateMinChanges) can be set per design document, a separate MB MB-11595 was raised to change the documentation. http://docs.couchbase.com/couchbase-manual-2.5/cb-admin/#automated-index-updates

This code is at http://src.couchbase.org/source/xref/2.5.1/ns_server/src/set_view_update_daemon.erl#103