MB-8348: implemented option for compactor's --evict flag

Change-Id: I505a21e2e1d8a517c4cd47de02fa82b6c8199874
Reviewed-on: http://review.couchbase.org/26526
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>
Reviewed-by: Aaron Miller <apage43@ninjawhale.com>
Tested-by: Aaron Miller <apage43@ninjawhale.com>