Fix egs++ 3ddose output and change getMass to getVolume

[MartinMartinov]

The egs_base_geometry getMass virtual function is exchanged with
a getVolume function that returns region volume instead of mass.
This change was performed because typically, initGeometry() is
invoked before any media data is read in egs_applications, thus
getMass' dependence on medium data could be unreliable. The
getMass function was thus replaced with a getVolume function,
which only relies on internal gemoetry definitions to return a
value.
The geometries in egs_autoenvelope, egs_nd_geometry, egs_rz,
and egs_spheres are affected. The ausgab dose scoring object
which outputs a 3ddose file was also changed to reflect the
change from getMass to getVolume. This modification of
egs_dose_scoring also now includes relativeRho in the mass
calculation.

[MartinMartinov]

I've tested the changes to egs_nd_geometry and egs_dose_scoring by comparing an ausgab object 3ddose file with egs_chamber results (where I calculate mass by hand), and I get the exact same dose and uncertainty per voxel. I have also performed checks of all of the geometries that were changed using egs_brachy, which was also changed to modify to use getVolume instead of getMass, and things seems to be working well.

[rtownson]

We need to merge this in asap. It could include one more change, while we're at it:

--- a/HEN_HOUSE/egs++/egs_advanced_application.cpp
+++ b/HEN_HOUSE/egs++/egs_advanced_application.cpp
@@ -1171,7 +1171,8 @@ void EGS_AdvancedApplication::resetRNGState() {
 //************************************************************
 // Returns density for medium ind
 EGS_Float EGS_AdvancedApplication::getMediumRho(int ind) {
-    return the_media->rho[ind];
+    // Handle a negative index for vacuum
+    return ind < 0 ? 0.0 : the_media->rho[ind];
 }

I just don't have permission to push to Martin's branch.

[ftessier]

Rebased on develop, no conflict.

[ftessier]

Applied astyle, only whitespace changes.

[MartinMartinov]

Rebased on develop, no conflict.

Honestly, a little surprised, but I'll take it. :)

[ftessier]

Surprised that there is no rebase conflict, or that it is being merged in? 😆

[ftessier]

Added Reid's patch (see above); changed ternary if-expression to if-statement. To squash before merging.

[ftessier]

Squashed the commits and fix typo in commit message. No code change.