Implement forward euler for lean angle estimate.

Estimate lean angle using forward euler method with accelerometer,
gyroscope measurements.
Use full state feedback without state estimation.

Use measurements directly in full state feedback. Calculate lean, steer
rate using forward euler, derivative filter.
Merge remote-tracking branch 'oliverlee/fullorderobs' into full_order_observer
First quasi successful runs.

025.dat, 026.dat, 027.dat of 27JUN2013.
Two more quasi successful runs, 028.dat, 029.dat.

Going to revert the change and try only changing R so that we remove
saturation.
Runs 030.dat, 031.dat, 032.dat.
Run 033.dat through 037.dat of 28JUN2013.
Add LED indicators when lean and steer angles are small.

The purpose of this commit is to turn LED indicator lights on when the bike is
very close to the reference configuration; the hope is that by starting each
run at nearly the same initial configuration, we can obtain more consistent
behavior.