Summary:
This diff makes sure that errors are propagated similarly in flipper desktop and browser version, and that they are shown in either case.
Since in the browser version, the UI loads after the error happened, we'll store the error so that any client connecting in the future will read and report it.
Also added a `--failFast` flag to flipper-server, so that the process exits immediately if misconfigured, which is convenient in CI use cases and such
Reviewed By: nikoant
Differential Revision: D33348922
fbshipit-source-id: 0f584104f881141fde38da3f0031748415343ea2