Automated image builds for registry

By using CI, builds can be scheduled and the process is unambiguous.

Fixes #2 (closed)

Incidentally, fixed #3 (closed) as part of overall cleanup.

README.md

-Docker Images
-=============
+# Docker Images [![pipeline status](https://git.ethitter.com/docker/images/badges/master/pipeline.svg)](https://git.ethitter.com/docker/images/commits/master)
 
-A collection of images used with GitLab CI
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+A collection of images used with GitLab CI, built using GitLab CI. ♾
+
+## Use
+
+See this project's container registry for available images.