modified detector geometry slightly
lead shield and CH Scintillator are used now
photonresponse works (almost perfect)

	modified:   include/NSDetectorConstruction.hh
	new file:   questions
	modified:   src/NSDetectorConstruction.cc
	new file:   src/NSMaterialConstruction.cc
	modified:   src/NSSD.cc
	new file:   todo
	modified:   vis.mac