Fix #295 overwrite existing ground material
Fix #295 overwrite existing ground material

Shortened code, fixed EOL errors. Satisfies testing of new mat, overwrite new mat, overwrite old mat, setting ground to overwrite of new and old mats.

NREL/bifacial_radiance,NREL/bifacial_radiance,NREL/bifacial_radiance,NREL/bifacial_radiance