separate container for nginx, multi stage build

[sergerdn]

There are big changes. Important things are:

• nginx started from separated container, because some people do not need nginx inside
• every container have image with name and version. e.g.:
  • image: "postgres:13.1-alpine"
  • image: "redis:alpine3.12"
• env files not tracked by git
• every container restart: on-failure
• using 2 stages to build lemur:
  • stage builder
  • stage build docker app
• lemur using python env, because stages

Last thing help us to keep our Docker images small. Have a look https://docs.docker.com/develop/develop-images/multistage-build/#use-multi-stage-builds

Docker Image size(lemur):

• before changes 462M

• after changes 156M plus new alpine nginx container

  P.S. I'm not very experienced with docker, so any suggestions will be much appreciated.

[sergerdn]

Work done, ready for review.