Fix #9: Increase array defaults, decrease EPSEMFP

[rtownson]

This PR contains a number of suggestions that are up for discussion! There is a tradeoff for compatibility with old systems in moving to larger default array sizes.

1. Increase a number of array size defaults, since modern systems have considerably more memory on average than they used to.

2. [Edit: I took this change out, so radiative compton corrections are off by default] Enable radiative compton corrections in all applications. This one is up for debate! From what I understand it requires increasing the stack size, which I have done only for egs_chamber so far in this PR. Should I also increase the stack size for all applications, and do we want this on by default?

3. Decrease EPSEMFP and EPSGMFP, fixing issue Seg fault with BEAM shared library in DOSXYZnrc with modern gcc versions #9.

These changes are mainly quality-of-life improvements for users who typically had to make the adjustments manually. Thanks to @ojalaj for providing a list of suggestions.

[mainegra]

@rtownson all these changes should definitely be made. I can see that in egsnrc.macros $MXSTACK is only 40. We should definitely increase it although a matter of discussion would be how large. Although memory is readily available these days, we shouldn't be wasteful either.
Regarding the radiative corrections, I agree that right now it is slightly cumbersome to turn them on. If we can prove that having them on by default won't significantly affect simulation efficiency, then we turn them on by default. But if there is a significant penalty in CPU time, given that they have little impact on the results of most cases then keeping them as an option is the way to go. The idea of providing parameter sets for different scenarios comes to mind .... ;-)

[blakewalters]

@rtownson: I like these changes to the defaults (max. no. of media = 7! Phwaat?), but I'm with @mainegra on changing the default setting of radc_flag. At what energies and for what simulation geometries is this required?

[ojalaj]

Why not increasing MXSTACK also in egs_chamber?