Split the controller into multiple processes

[tkaitchuck]

Problem description
Right now the controller is a single service that performs multiple loosely related jobs: Scaling, TransactionManagment, Metrics, Discovery, etc.

All of these are linked in some way to one of the other jobs so they cannot be naively split up, but taken together it ends up combining a lot of diverse code into a single process.

Problem location
Controller

Suggestions for an improvement
Step back and carefully look at the design. Perhaps there is a way we could split the service up into multiple different services.

[tkaitchuck]

Issues like #1436 and #1210 would be a lot easier to solve if we had a process that could store metadata.