build-osv-release: OSv memcached server

This adds our own memcached server to an OSv release that is pushed to
Capstan S3 repository.

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
build-osv-release: OpenJDK/OSv base image

Add a OpenJDK/OSv base image for developers who want to use Capstan to
package and run their Java applications.

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>