MB-7629 Add native viewgroup compactor

Implementation of native view index compactor.
The native program receives viewgroup header info through stdin
and it creates a new index file and recreates all view btrees
and id btree. The resulting index header is written out to stdout.

Change-Id: I0c9c9ff33d3e005f22cc848c85d708b158d806e4
Reviewed-on: http://review.couchbase.org/31666
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>
Tested-by: Filipe David Borba Manana <fdmanana@gmail.com>