Use packages, clean up code etc

[jml]

From @tomwilkie

Copied from original issue: tomwilkie/frankenstein#15

[jml]

From @jml

@tomwilkie This will need a better description if someone else can attempt it.

[jml]

From @tomwilkie

I guess we probably want a package for each component - ingestor, distributor, querier?

And by code cleaner I just mean removing TODOs, adding unit tests, improving code smells, better decoupling, be more stringent in code reviews.

[jml]

From @jml

OK. I suggest we make the package-per-component bit the thing for this ticket and do the other stuff incrementally as we make other changes.

[jml]

From @tomwilkie

Agreed!

[tomwilkie]

Status:

• the chunk store etc has been put in a separate package
• the ring & consul stuff is in a package

Todo:

• put distributor code in a package
• copy ingester code into here, in a new package (see More code organisational cleanups #20)
• [ ] get the querier changes upstream, pipe through contexts etc - @juliusv is working on it - is there a issue for this? (Potentially replace parts of Cortex's remote querying code with upstream code once it exists #5)