Implement review notes multiple_devices

[steersbob]

File: multiple_devices.md
Commit: 5be4c2c
Review date: April 12 2021

l4: Suspected Dunglish, revise: "This page explains how Brewblox service configuration works."

l9: "..designed to control.."

l30: "split the software into services, see diagram below"

l32: "graphs. The device services are used to control individual devices." - are there more types of services?

l34: How honest and open do we want to be? I could use some explanation: "Every device type needs it's own software service. These devices are supported out of the box:"

l71: "You can find the file in your brewblox\ folder."

l123: 'Docker-compose service sytax' feels like a subsection of 'Adding devices' but has the same heading... a bit weird. Also: 'Adding devices' has no other subsections.

l127: My docker-compose.yml is ordered slightly different:
spark-one:
command: --name=spark-one
image: brewblox/brewblox-devcon-spark:${BREWBLOX_RELEASE}
privileged: true
restart: unless-stopped

l135: Ah, the order might be changed for the story...

l145: Add a few words and emphasis: "This is like the examples of short service configurations we saw earlier. The two most important settings in a service configuration are its name (spark one), and its type..."

l147: can you have multiple spark services with different images? Maybe when connecting different Spark versions to the same server? Can ppl write / change their own image to their liking?

l179: Weird the chapter ends here. Maybe add the chapters: adding a spark service and adding a Spark simulation to the same file in the 'adding devices' section. When you want ppl to find these sections directly from the menu, just put a link there. I might expect information on adding the tilt, etc. here too... Explicitly point to the respective readme files on git maybe?