Update observer state before estimation start.

Continuously update the observer state with measurement data (steer,
lean rate, steer rate) while not estimating.
Move legend to upper left corner in plots.
Record desired steer and rear wheel motor currents.
Fix nasty little sign of torque and current bug.
Add encoder.steer_rate to lower subplot of plot_estimate().
Merge remote-tracking branch 'oliverlee/fullorderobs' into full_order_observer
Record motor torque instead of motor current.
Initial conversion from greek names phi and delta to lean and steer.