Switched default to non-ideal positioning of PXL volumes (currently this affects active layers only). The change assumes that the user runs StPxlDbMaker to create the dataset with appropriate transformations
StiDetectorBuilder: Added method to remove a previously added Sti detector/volume
StiDetectorBuilder: Modified detector accessor to handle invalid detector requests in somewhat more graceful way
Uniform improvements in Sti objects output streamers
Remove unused variables
Added new data member to keep track of track energy losses in the node