Debian Sid based base-image for building docker images.

Inherits from debian:sid. Configures apt to not install recommended and
suggested packages. Installs following packages often required for
development:

    locales, build-essential, curl, openssl, ca-certificates

Add readme for Debian base-image.
Add readme for Debian base-image.

Signed-off-by: Anurag Priyam <6e6ab5ea9cb59fe7c35d2a1fc74443577eb60635@gmail.com>
