NewRadX boundary condition conflicts with symmetry condition

[Roland Haas]

NewRadX’s radiative boundary condition conflicts with reflection (and periodic and others) boundary condition since both end up being applied at the same time producing unexpected results.

Patches to Loop and NewRadX are:

https://github.com/EinsteinToolkit/CarpetX/pull/300

and

https://github.com/EinsteinToolkit/SpacetimeX/pull/39

[Roland Haas]

Please review.