Clean up ChBody.h comments.
Clean up ChBody.h comments.

Provide more explicit details on setting body inertia properties.

dariomangoni/chrono,jcmadsen/chrono,armanpazouki/chrono,jcmadsen/chrono,jcmadsen/chrono,jcmadsen/chrono,rserban/chrono,rserban/chrono,dariomangoni/chrono,dariomangoni/chrono,projectchrono/chrono,dariomangoni/chrono,armanpazouki/chrono,rserban/chrono,dariomangoni/chrono,projectchrono/chrono,andrewseidl/chrono,rserban/chrono,projectchrono/chrono,rserban/chrono,amelmquist/chrono,armanpazouki/chrono,amelmquist/chrono,projectchrono/chrono,andrewseidl/chrono,Milad-Rakhsha/chrono,amelmquist/chrono,Milad-Rakhsha/chrono,tjolsen/chrono,tjolsen/chrono,armanpazouki/chrono,andrewseidl/chrono,jcmadsen/chrono,amelmquist/chrono,projectchrono/chrono,andrewseidl/chrono,Milad-Rakhsha/chrono,projectchrono/chrono,Milad-Rakhsha/chrono,amelmquist/chrono,amelmquist/chrono,andrewseidl/chrono,dariomangoni/chrono,Milad-Rakhsha/chrono,rserban/chrono,tjolsen/chrono,jcmadsen/chrono,Milad-Rakhsha/chrono,jcmadsen/chrono,armanpazouki/chrono,tjolsen/chrono,armanpazouki/chrono,tjolsen/chrono,rserban/chrono