DBW: Increase manual brake torque to 700 Nm to stop Carla

[edufford]

Udacity testing showed that Carla needs about 700 Nm brake torque to fully stop, so manual brake torque values need to be adjusted for this.

• Increase manual brake torque amount to 700 Nm and add increase rate limit for smooth apply (tuned for ~1 sec apply in simulator).
• Adjust site test launch parameter decel_limit from -1 (428 Nm) -> -2 m/s^2 (857 Nm) to allow 700 Nm manual brake torque.
• Filtered full-brake release from 700 Nm takes longer, so increase filter cut-off from 10 Nm -> 50 Nm to reduce the release time to compensate.