Separate placement calls in the VolumeManager and distinguish between DetElement placements and Volume placements (currently unused)

DetectorData: Warn if a second object (e.g., constant) is created, as insert will not overwrite the existing one

this constructor registers the shape with the geoManager

Default constructor of TGeoConeSeg (or any other TGeoShapes) do not
register the object so they are not automatically cleaned up. So we
call the constructor with parameters instead

the if condition was never true so 'elif' was never executed by cmake or an error would have been raised

Fixes issue that CMAKE_CXX_COMPILER_ID was not AppleClang on MAC

_wtM was never cleaned, use unique_ptr for automatic cleanup
explicitely delete default ctor, copy ctor and assignment operator