The new probe will convert all node's LatestControls to Controls, so
the old app can consume them. Also, the new app will convert all
node's Controls to LatestControl, so it can consume the reports from
old probes.
- Add interfaces to allow for alternative implementations for Collector, ControlRouter
and PipeRouter.
- Pass contexts on http handlers to these interfaces. Although not used by the current
(local, in-memory) implementations, the idea is this will be used to pass headers to
implementations which support multitenancy (by, for instance, putting an authenticating
reverse proxy in form of the app, and then inspecting the headers of the request for
a used id).
