Add a Docker Compose manifest for local testing

Context

BuildGrid's already ships a Dockerfile manifest for local development. Would be nice to also ship a docker-compose.yml manifest that would:

• Run BuildGrid (at least) three different containers:
  • A controller container for the execution service.
  • A storage container for CAS and ActionCache.
  • One or more bots.

Ideally, and as the target is local development and testing, the controller and storage services would be accessible from the host.

Task Description

• Update/Adapt the existing Dockerfile manifest.
• Introduce a docker-compose.yml manifest.

Acceptance Criteria

Run Buildgrid locally, and scale the number of bots, is as simple as invoking docker-compose up.