Add version tag to Docker builds

[matthewhartstonge]

Hi team!

We are currently rolling with companion, but it's hard to know what version you are running due to using a time stamp as the container tag. As such, it would be nice to have semver tags the align with what is in the containers.

I noticed a container we lit up yesterday logged to console it's version v0.14.5-alpha.0. It would be great if your CI/CD process could tag the version as well.

uppy: 2018-10-17T03:24:57.687Z [info] jobs.cleanup.start starting clean up job
Welcome to Companion! v0.14.5-alpha.0
Listening on http://0.0.0.0:8090

From a developer perspective, this also makes it easier to know what API is running on the tin rather than having to cross reference a timestamp/load up a container to work it out.

[kvz]

/cc @kiloreux

[kiloreux]

#1579

[arturi]

Please re-open if #1579 doesn’t solve this. Thanks @kiloreux!