Enable Docker technology in COIN for Qt MCU

Background

MCU project will use docker technology to encapsulate build environments for different hw platforms.
The idea is that the docker images would be generated in ci and uploaded to a server (docker registry) for all developers to download and use.
The docker images would also be reused in ci if the dockers content has not changed.
Docker technology was chosen because the images are smaller than complete virtual machine images.

Requirements (draft)

• a way to define a "Dockerfile" for each platform (combination of hw, target os and compiler) in qtformcu repo
• building a docker image based on the "Dockerfile" (like provisioning)
• uploading docker image to a server (docker registry)
• reusing existing docker images if the docker content has not changed
• launching a docker container from a docker image
• build the mcu inside the docker container, store results and report back
• test the mcu inside the docker container, store results and report back