more changes to configure redis using environment variables

DOCKER.md

...rc/main/scala/org/bigbluebutton/SystemConfiguration.scala

...rc/main/scala/org/bigbluebutton/SystemConfiguration.scala

...rc/main/scala/org/bigbluebutton/SystemConfiguration.scala

bbb-common-message/Dockerfile

bbb-common-web/Dockerfile

...in/scala/org/bigbluebutton/api2/SystemConfiguration.scala

bigbluebutton-html5/imports/startup/server/redis.js

bigbluebutton-web/Dockerfile

bigbluebutton-web/docker_wrapper.sh

labs/bbb-webrtc-sfu/config/custom-environment-variables.yml

labs/docker/sbt/Dockerfile

nginx.conf