Added docker-compose.yaml, more BUILD-ARGS for the Dockerfile and documentation

[Rom3dius]

As the title says:

• Added docker-compose.yaml
• HealthCheck in docker-compose.yaml
• Build arguments in docker-compose.yaml
• Added REPO build args for both client and node
• Added COMMIT build args for both client and node
• Added documentation pertaining to all of the above in docker/README.md

Reasoning behind these build arguments and docker-compose: Allows for easing testing of new and existing apps/contracts/workflows on all versions (including forked versions) of the node and it's software. For example, @jonas089 has a fork of casper-node implementing host functions needed to test kairos.