Add celer-geo app for visualizing geometry (#1201)
Fix polar angle sampling and Mott factor in Wentzel distribution (#1212)* Update Wentzel distribution test results and use VEC_SOFT_EQ intead of SOFT_NEAR* Add lower energy point in Wentzel distribution testFails with:```BernoulliDistribution.hh:69:celeritas: precondition failed: p_true >= 0 && p_true <= 1"```* Fix Mott factor and update tests* Fix sampling of cos theta and update test* Remove Coulomb scattering 100 MeV low energy limit and test more incident energies