Rename orientation sample to accelmag

Preparing to use the current gyro sample as the main orientation
sample.  This one just shows what can be done with the accelerometer
and magnetometer with some moving average low-pass filtering.
Rename accelmag main .pde as well
Rename gyro sample to orientation

This sample which can perform Kalman filtering in addition to just
using the unfiltered accelerometer, magnetometer, and gyro
measurements is now the main orientation Processing sample.