Thanks! I caused some conflicts with this, so I've rebased your branch over master and fixed up.

I also changed this to pass an empty title:

this.sendEvent(new ProgressStartEvent(debugLaunchProgressId, "", "Launching..."));

It's not clear if this is allowed (the spec says title is mandatory), but I've filed microsoft/language-server-protocol#1025 for clarification. If it's not allowed, I think there should be a way to allow us to have single-message updatable progress without needing to have two messages joined with colons.