SLG4: initial work on Metal2 material

--HG--
branch : slg3.5_startup
rename : scenes/luxball/luxball-hdr-glossy2.cfg => scenes/luxball/luxball-hdr-gold.cfg
rename : scenes/luxball/luxball-hdr-glossy2.scn => scenes/luxball/luxball-hdr-gold.scn
SLG4: finished the work on Metal2 material (cpu-only)

--HG--
branch : slg3.5_startup
rename : scenes/luxball/luxball-glossy2.cfg => scenes/luxball/luxball-copper.cfg
rename : scenes/luxball/luxball-glossy2.scn => scenes/luxball/luxball-copper.scn