Add MCKineticsObserver and TiltObserver

[ArnaudDmt]

The KineticsObserver is an MEKF-based (Mulitplicative Extended Kalman Filter) estimator that relies on a visco-elastic model of contacts to estimate the following variables: the pose of the robot in the world, its velocity, the external wrench applied on the centroid, the bias on the gyrometer bias, and the contact wrenches and pose.

The TiltObserver is based on a complementary filter which estimates the tilt and the local velocity of the IMU.

Also adding NaiveOdometry, that can be called after updating the realRobot with another estimator. It uses the estimated tilt to perform an odometry based on the successive contacts (that we also call legged odometry), giving a pose in the world. This method assumes that contacts are subject to no slippage.

Both observers can perform either:

• no odometry: the estimated robot remains attached to the control robot.
• flat odometry: the TiltObserver will perform a legged odometry using its estimation of the tilt of the robot. The Kinetics Observer will use its visco-elastic model to correct the contacts pose and is therefore more robust to slippage. This odometry mode will consider that the contacts are always on a height z = 0m, which allows a more accurate estimation on flat grounds.
• 6d odometry: The height constraint for the contacts is not applied here so the odometry can be performed on non-flat environments.