Latch is used differently across apps and may be overwritten

[rtownson]

Some of the egs++ apps and tools, such as egs_kerma and egs_fluence_scoring, may overwrite a particle's LATCH. Generally, this is not an issue. However, since adding egs_phsp_scoring it is conceptually possible that a user could assign LATCH in BEAMnrc, use the phase-space in egs_kerma, generate an output phase-space, and then want to analyze the LATCH again. Or, the user may use both egs_fluence_scoring and egs_phsp_scoring in the same simulation. Therefore, we should consider how to safeguard the use of LATCH across EGSnrc.

Suggestion:

• Reserve LATCH for the BEAMnrc definition. Any new usage should employ a different parameter that we add. For example, see the_extra_stack->nbr_splitting for egs_chamber.
• Consider if egs_phsp_scoring is valid for all of the apps.