smaccmpilot: Remove "stabilize" app.
stabilize_hil: Build HIL and non-HIL images.

- Removed obsolete "gcs" module.
- Read sensors unless USE_HIL is defined, then read them from GCS.
stabilize_hil: Reverse pitch on input to stabilization.

- Pitch control was backwards.  This seems like the correct place
  to flip the sign.
smaccmpilot: Use UART5 for GCS communication.
smaccmpilot: Tune PI gains for ARDrone motors.
smaccmpilot: Split initialization from starting of tasks.

- If we start a module's task when it is initialized, it may start
  running before the other modules are ready.  This leads to
  crashes when they try to take semaphores that haven't been
  created yet.
- Initialize all modules first, then start all the tasks.