Refactored joint limit avoidance for SingleChainManipulability

...ot/IK/CompositeDiffIK/ManipulabilityNullspaceGradient.cpp

...obot/IK/CompositeDiffIK/ManipulabilityNullspaceGradient.h

...alRobot/Manipulability/AbstractManipulabilityTracking.cpp

VirtualRobot/Manipulability/AbstractManipulabilityTracking.h

VirtualRobot/Manipulability/BimanualManipulability.cpp

...alRobot/Manipulability/BimanualManipulabilityTracking.cpp

VirtualRobot/Manipulability/BimanualManipulabilityTracking.h

VirtualRobot/Manipulability/SingleChainManipulability.cpp

...obot/Manipulability/SingleChainManipulabilityTracking.cpp

...lRobot/Manipulability/SingleChainManipulabilityTracking.h

VirtualRobot/examples/RobotViewer/DiffIKWidget.cpp