Modified testActuatorsCombination
Added the option that user can select the location of applied force and its frame
(default: origin of the body expressed in body's frame)
Changes to make namings for point/axis frames consistant
(with PrescribedForce whcih uses similar assumptions,
default: point of application is in body frame, spatial forces
are expressed in global (ground) frame).
Tetting get_point propoerty in testActuatorsCombination