CBD-1461: Support Sherlock builds on Debian

Including new Docker image and build-script updates for .deb packaging.

Change-Id: I0661080b21c58436ca87a628d55592f40c23c700
Reviewed-on: http://review.couchbase.org/44174
Reviewed-by: Chris Hillery <ceej@couchbase.com>
Tested-by: Chris Hillery <ceej@couchbase.com>