Restructure the docker build to move docker content to docker folder.

Makefile

docker/Dockerfile

docker/build.sh

docker/etc/apt/sources.list.d/buster-backports.list

docker/etc/apt/sources.list.d/google-cloud-sdk.list

docker/etc/apt/sources.list.d/local.list

docker/etc/apt/sources.list.d/stanford.list

docker/etc/default/slapd

docker/etc/krb5.conf

docker/etc/ldap/ldap.conf

docker/etc/ldap/sasl2/slapd.conf

docker/etc/saslauthd.conf

docker/start.sh