Publishers: stdout and AMS

[enolfc]

Summary

This PR brings pluggable support for the output. 2 initial publishers are provided: stdout (the one we already had) and ams for pushing messages to ARGO AMS

[enolfc]

AMS support is broken in python3 :(
Could just use requests instead, but need to check the actual API calls needed for that.

[gwarf]

Thanks, looks great!
Could you please add some documentation before we merge this?
And what is the status of tests?
Last point, should we release a version before this is merged, or should we wait for it?

[enolfc]

Thanks, looks great!
Could you please add some documentation before we merge this?

yes, will do in a subsequent commit

And what is the status of tests?

I'm now testing with the catch-all stuff, will check with AppDB if they are still getting the same information
And some unit tests will be coming also to this repo

Last point, should we release a version before this is merged, or should we wait for it?

I think is better to wait, as I want ONE providers to use this directly

[enolfc]

I believe now it's ready, @gwarf take a look when you can

[gwarf]

Looks good, a few small typos, maybe some doc strings on all new methods would be nicer, but it's fine with me.