Add MCX simulation reflection flag -b

[RecurvedBow]

Please describe your :rocket: feature request. Add the -b / --reflect flag to the MCX simulation without breaking any existing reflectance behavior (https://mcx.space/wiki/index.cgi?Doc/mcx_help).

Describe the solution you'd like Update the MCXAdapter to accept a boolean flag whether the photons should be reflected or transmitted at the simulation borders.

[RecurvedBow]

Will only apply reflection on the volume faces along the x-axis and z-axis

[RecurvedBow]

Since there are multiple possible behaviors, will define an enum instead of a boolean flag instead. Will include: default, fresnel reflection, mirror reflection, cyclic

[kdreher]

This issue is related to #286 and we'll wait until that one is resolved :)

[leoyala]

This could also be resolved by #311 since user-defined flags could be passed and would overwrite the default ones.

[RecurvedBow]

I have found out that the command flags for capturing reflectance are set incorrectly: we do not need --saveref; and there is actually a bug with saving photon direction and position on exit. I will address the first case in this issue, and add the second as a bug issue