synchronise use of Context

Core/include/Acts/Detector/DetachedTrackingVolume.hpp

Core/include/Acts/Detector/TrackingGeometry.hpp

Core/include/Acts/Detector/TrackingVolume.hpp

Core/include/Acts/Detector/detail/TrackingVolume.ipp

Core/include/Acts/Layers/Layer.hpp

Core/include/Acts/Layers/detail/Layer.ipp

Core/include/Acts/Tools/LayerCreator.hpp

Core/include/Acts/Utilities/Context.hpp

Core/src/Detector/DetachedTrackingVolume.cpp

Core/src/Detector/TrackingGeometry.cpp

Core/src/Detector/TrackingVolume.cpp

Core/src/Layers/PlaneLayer.cpp

Core/src/Surfaces/Surface.cpp

Core/src/Tools/CylinderVolumeBuilder.cpp

Core/src/Tools/CylinderVolumeHelper.cpp