We don't need two separate executors for long-running IO threads.

Fixed a bug in SimplexMessagingIntegrationTest that should've caught
this.

This ensures that if two DatabaseExecutor tasks update the database and
broadcast events, the events are broadcast in the same order as the
updates occurred.

Patched jtorctl to pass more information about circuit events to the
controller to help us debug connection problems.

This may have been the cause of bug #69. Removed the wait-for-shutdown
code in DroidtoothPlugin that was added to attempt to avoid that bug.