Write Dockerfile for OBP-API

[chrisjsimpson]

Is your feature request related to a problem? Please describe.

There is presently no in-repo Dockerfile (aka Containerfile) for OBP-API.

Describe the solution you'd like
As a developer I can build & run a container for OBP-API from within this repo.

Describe alternatives you've considered
It is best practice to keep container files within the same repo as their code where reasonable.

With this completed, the OBP-Docker repo should/must be deleted as redundant.

Additional context

See:

• https://github.com/tawoe/OBP-API/blob/2d7ef5c04e05aff09045c1cefb00d1ac99b40e50/Dockerfile#L1
• https://github.com/chrisjsimpson/obp-kubernetes/blob/master/Dockerfile (much older)

Be aware that layer caching is now a thing, the current attempts of the container file take a long time to re-build since there's no caching- this may be addressed with layer caching at build time.