Add a proof-of-concept minikube cluster

[dinowernli]

The current kubernetes configs (see kube directory) are proof-of-concept in the sense that they run a single almanac binary which runs all the services. This should be replaced/complemented with a kubernetes setup which runs each of the services separately. Rough outline:

1. Add supprt in the almanac binary for specifying via flags which services the binary should run. It should still be possible to run all services, but the common case will be to run a single one per binary by invoking something like ./almanac serve --appender_ports=123,124,125 --mixer_ports=456,457
2. Create a kubernetes service each for ingester, appender, mixer, and janitor.
3. As a proof of concept, the services should share a kubernetes volume which they all talk to using disk storage. A second step would be to have them all point to an actual s3/gcs bucket.
4. Teach service discovery to resolve services based on the kubernetes DNS names.