Added GHKFilterOrder class.

Added class that implements a g-h filter of order 0, 1, 2.
Add getter/setter properties for KF.

All matrices in KalmanFilter now have getter/setter. Allows me
to ensure all are the correct shape.
Added getter/setter properties to ExtendedKalmanFilter.

Moved all matrices to a _name naming convention, and added getter/setter
to enforce that each is created with the correct dimensions.