Adds get-methods to retrieve base, sine, and cosine msspolys from `TrigPoly` objects.
Adds get-methods to retrieve base, sine, and cosine msspolys from `TrigPoly` objects.

edowson/drake,psiorx/drake,crogers3/drake,crogers3/drake,crogers3/drake,scottviteri/drake,billhoffman/drake,manuelli/drake,edowson/drake,tkoolen/drake,sheim/drake,sheim/drake,hanssusilo/drake,hanssusilo/drake,billhoffman/drake,astrorog/drake,psiorx/drake,manuelli/drake,astrorog/drake,scottviteri/drake,astrorog/drake,sheim/drake,tkoolen/drake,billhoffman/drake,thientu/drake,psiorx/drake,crogers3/drake,tkoolen/drake,tkoolen/drake,thientu/drake,edowson/drake,edowson/drake,psiorx/drake,psiorx/drake,hanssusilo/drake,manuelli/drake,edowson/drake,astrorog/drake,billhoffman/drake,sheim/drake,thientu/drake,billhoffman/drake,tkoolen/drake,hanssusilo/drake,tkoolen/drake,sheim/drake,psiorx/drake,crogers3/drake,crogers3/drake,manuelli/drake,tkoolen/drake,sheim/drake,sheim/drake,scottviteri/drake,scottviteri/drake,psiorx/drake,astrorog/drake,manuelli/drake,astrorog/drake,scottviteri/drake,thientu/drake,billhoffman/drake,billhoffman/drake,astrorog/drake,psiorx/drake,thientu/drake,crogers3/drake,scottviteri/drake,manuelli/drake,crogers3/drake,hanssusilo/drake,edowson/drake,edowson/drake,hanssusilo/drake,thientu/drake,hanssusilo/drake,edowson/drake,thientu/drake,sheim/drake,billhoffman/drake,scottviteri/drake,manuelli/drake,hanssusilo/drake