Revisit and rewrite the control server

[directionless]

The control server is coming back! This is a fairly large project that needs a bunch of PRs. The end goal is to have launcher have a control channel to our K2 (our SaaS) which is used for controller and changing launcher's behavior.

Task:

• Enable the control server on windows. It's a no-op, but it'll improve code consistency. (small)
• Design and document a control protocol
• Authentication ??? Should it use the osquery node key (how?) or the launcher RSA keys?
• Table for server writable data #936

Some likely control things. Not totally sure how these will shape up:

1. enable/disable desktop
2. Change update channel
3. Re-trigger the updater, not just via callback

[directionless]

This is done and live