This is a first take at a detector for the HMolPol system.  It is made
from a "dummy" scintillator I found online (used only for testing) it
will be changed with something more realistic later.  

These detectors:
-  are placed 3.0 m down stream from the center of the Hydorgen target.
-  are 4 x 4 cm square (in X vs Y) and 2 cm thick.  T
-  have a center that is 0.2 m away from the z axis (or the center of
the beam line)
change the material of this dummy sensitive detector to G4_AIR
added in the detector.gdml file which places on of these detectors left
(x = -0.2 m, y = 0 m) and right (x = 0.2 m, y = 0 m) of the beam line
with a central position 3.0 m down stream from the center of the
Hydrogen target