Revert "Remove Kalman filter again, unsuitable for nonlinear systems"

This reverts commit d20c56f439c05528967b2bc408a6594a5605675e.

With best regards to dbaarda :-)

Conflicts:
	CMakeLists.txt

Signed-off-by: Stanislaw Halik <sthalik@misaki.pl>
prevent redefinition warning

Signed-off-by: Stanislaw Halik <sthalik@misaki.pl>
accela: implement a third-order highpass filter

Signed-off-by: Stanislaw Halik <sthalik@misaki.pl>