WIP: meta logging, logging by service tag and more

[sas1024]

Hello!
I've improved your fork:

1. Use go modules
2. Use docker multistage build
3. Use latest nomad API library.
4. Add logging by service tag. It's need to log only services you want, not all services.
5. Add job meta and task meta to log. It's need to add some additional info to log from tasks.

I hope, this changes will be useful.

[dmwilcox]

Oh no! I've just now seen this. I can review hopefully soon but let's try and get this upstream to adragoset's repo too.

[sas1024]

@dmwilcox 👍👍👍