Revise pose covariance representation (to PoseManifoldGaussian)

source/RobotAPI/interface/objectpose/object_pose_types.ice

source/RobotAPI/libraries/ArmarXObjects/CMakeLists.txt

source/RobotAPI/libraries/ArmarXObjects/ObjectPose.cpp

source/RobotAPI/libraries/ArmarXObjects/ObjectPose.h

...RobotAPI/libraries/ArmarXObjects/PoseManifoldGaussian.cpp

...e/RobotAPI/libraries/ArmarXObjects/PoseManifoldGaussian.h

...e/RobotAPI/libraries/ArmarXObjects/ProvidedObjectPose.cpp

source/RobotAPI/libraries/ArmarXObjects/ProvidedObjectPose.h

...e/RobotAPI/libraries/ArmarXObjects/forward_declarations.h

source/RobotAPI/libraries/ArmarXObjects/ice_conversions.cpp

source/RobotAPI/libraries/ArmarXObjects/ice_conversions.h