add cubemaps to the management, fixes #5047 (#6323)
add cubemaps to the management, fixes #5047 (#6323)


NathanSweet/libgdx,Zomby2D/libgdx,stinsonga/libgdx,cypherdare/libgdx,Zomby2D/libgdx,bladecoder/libgdx,bladecoder/libgdx,tommyettinger/libgdx,tommyettinger/libgdx,NathanSweet/libgdx,Zomby2D/libgdx,bladecoder/libgdx,stinsonga/libgdx,NathanSweet/libgdx,tommyettinger/libgdx,tommyettinger/libgdx,bladecoder/libgdx,cypherdare/libgdx,NathanSweet/libgdx,cypherdare/libgdx,cypherdare/libgdx,stinsonga/libgdx,Zomby2D/libgdx,stinsonga/libgdx,libgdx/libgdx,NathanSweet/libgdx,tommyettinger/libgdx,libgdx/libgdx,stinsonga/libgdx,libgdx/libgdx,libgdx/libgdx,cypherdare/libgdx,Zomby2D/libgdx,libgdx/libgdx,bladecoder/libgdx