Fix docker-compose recipes

[chbrandt]

There is a bit of duplicated, outdated code in-and-around docker-compose files. Things to improve:

• use .env file instead of env.rc for docker-compose seamless use
• use docker-compose recipes inheritance mechanism (docker-compose.yml -> docker-compose.awstats.yml -> docker-compose.full.yml)
• move docker-compose build instructions to docker-compose.yml

[msdemlei]

@chbrandt, could you check whether PR #21 suitably addresses your concerns.