It's quirky, we have to pass the stopped event to LoadThreads so that it
can correctly work out the state of any _newly_ added threads. We now
also correctly apply the allThreadsStopped=False behaviour where you
must not allow expansion of such threads (in theory, that's untested).
- don't clear the stack trace on continue - track running status
properly (ish)
- mark threads (running) when the app is executing
- indicate the "current" thread with a different icon
TODO:
- allow user to specify current thread?
- track running status of threads individually?
- allow to pause/continue specific threads?
