Scheduler reconnects

* Update the scheduler to reconnect to the controller if there is an error or if the channel closes, waiting 1 second if more than one connection attempt has been made since the last update
* Add `ExpandedFormation.UpdatedAt` so that the scheduler can ask for only the updates since the last formation it received an event for
* Make deleted formations appear to have no processes so that the scheduler will remove it's processes if necessary
`StreamFormations` returns a `*error`, so this should never be `nil`. Check it after `ch` has closed, and the `range` ends (which will be immediately if the RPC fails).