TFoam support for MC event generator

[wdconinc]

There is already an event generator that takes MC output files and generates events starting from those events as input (e.g. factorization of lead wall showering and post lead wall optical simulation for pion detector). This suffers from limited event statistics unless we recycle events.

TFoam would be able to generate by x,y,z,theta,phi,E distributions representative of those events.

Other uses:

• Pre-scattering energy loss as simulated by Geant4 itself: run delta(E) beam into the target in a separate simulation, store all hits in target volume, pick and interpolate according to proper energy loss distribution. This would get away from models for energy loss implemented in our code and instead rely on the physics available in Geant4 materials definitions.
• Fast optical generation: run flat electron field in x,y,theta,phi onto a single quartz module, store resulting PE distribution, then run non-optical simulations and interpolate without need for optical simulation while still getting distribution correct. Full simulations are always possible, but the idea is that this would be 1000 times faster.

[wdconinc]

Would also be useful for #1.