Dockerfile is not reproducible

Using an unversioned 3rd party image as the base for this container makes the resulting container image dependent on what the upstream 3rd party put in the latest version of their container.

FROM continuumio/miniconda3

The OSSR should publish a policy for creating reproducible containers.

1. The FROM statement should include the full registry URL

   FROM docker.io/continuumio/miniconda3

2. The FROM statement should reference a specific version of the base container

   FROM docker.io/continuumio/miniconda3:4.10.3p0

3. The FROM statement should reference base container in a repository maintained by an EU funded provider, not a commercial organization

Should the OSSR maintain a registry of base container images for participants to use ?