MB-9771 Exchange viewgroup header via stdin/stdout

For view index incremental updater, change has been made
to receive viewgroup header via stdin and send back new header
after performing incremental updates via stdout. This avoids
writing of intermediate index header from native updater.

Change-Id: I68aecd2cb305a45a46f3d3fb45c705f2eab72ccc
Reviewed-on: http://review.couchbase.org/31361
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>
Tested-by: Filipe David Borba Manana <fdmanana@gmail.com>