Add basic redis setup for rate limiting

[GraemeHarris]

As per #175 redis setup to be used for rate limiting - maybe BE cache down the line.

I have updated the docker compose file to include redis + redis insights. They're quite basic for now with a lot of settings that can be tweaked as per need / feedback.

Ansible changes might need more testing

[yk]

also, some merge conflicts

[yk]

could you remove the ansible part? so we can get this merged. can you also make a new issue for including redis in ansible? I'll take that myself and do it later.

[andreaskoepf]

@yk is this ready for merge?

[kiritowu]

@GraemeHarris do you intend to add redis (and redis-insights) to Line 7 in the docker-compose.yml such that both redis and redis-insights will be started up for backend-dev purpose?

  backend-dev:
    image: sverrirab/sleep
    depends_on: [db, adminer, redis, redis-insights]

[yk]

Thank you!