Previously, the Octo docker image was not buildable by the standalone
Dockerfile; but relied on outputs from the Ubuntu pipeline. It was also
488MB, and had a host of other problems:
- Rocto was not bound to 0.0.0.0, but rather to 127.0.0.1, so you
  couldn't access it except using NAT routine, which doesn't work on
  non-Linux docker hosts.
- Instructions told the user to run the image interactively, but the
  entrypoint was for a daemon.
- The default DockerHub tab of "latest" (usually expected by end users)
  was missing; only "latest-master" was available.
- CTRL-C didn't work in case of direct daemon invocation.

To fix these:
- `Dockerfile` was modified to be standalone.
- Artifacts produced used in previous `Dockerfile` in `tools/ci/build.sh`
  removed.
- Remove now unused `tools/ci/docker-install.sh`.
- Update `tools/entrypoint.sh` to create a database if a user passes in
  a database; enable CTRL-C.
- Remove docker instructions found in `doc/intro.rst` and create new
  instructions in `README.md`.
- Gitlab pipeline now pushed `latest` instead of `latest-master`, using
  the `:latest` YottaDB, rather than the `latest-master` YottaDB.
- Final image is 335MB.