Cleanup CMakeLists
Cleanup CMakeLists

- rearrange source file groups
- for MSVC, collect all Bullet files into a nested group under 'collision'

projectchrono/chrono,jcmadsen/chrono,PedroTrujilloV/chrono,amelmquist/chrono,rserban/chrono,Milad-Rakhsha/chrono,dariomangoni/chrono,tjolsen/chrono,rserban/chrono,Milad-Rakhsha/chrono,jcmadsen/chrono,andrewseidl/chrono,PedroTrujilloV/chrono,Bryan-Peterson/chrono,andrewseidl/chrono,hsu/chrono,armanpazouki/chrono,Milad-Rakhsha/chrono,andrewseidl/chrono,hsu/chrono,dariomangoni/chrono,rserban/chrono,projectchrono/chrono,hsu/chrono,Milad-Rakhsha/chrono,hsu/chrono,andrewseidl/chrono,jcmadsen/chrono,rserban/chrono,tjolsen/chrono,Milad-Rakhsha/chrono,PedroTrujilloV/chrono,rserban/chrono,dariomangoni/chrono,dariomangoni/chrono,Bryan-Peterson/chrono,amelmquist/chrono,PedroTrujilloV/chrono,projectchrono/chrono,projectchrono/chrono,projectchrono/chrono,Milad-Rakhsha/chrono,armanpazouki/chrono,rserban/chrono,jcmadsen/chrono,tjolsen/chrono,dariomangoni/chrono,projectchrono/chrono,jcmadsen/chrono,amelmquist/chrono,amelmquist/chrono,armanpazouki/chrono,armanpazouki/chrono,dariomangoni/chrono,andrewseidl/chrono,Bryan-Peterson/chrono,amelmquist/chrono,armanpazouki/chrono,Bryan-Peterson/chrono,tjolsen/chrono,jcmadsen/chrono,tjolsen/chrono,armanpazouki/chrono,Bryan-Peterson/chrono,jcmadsen/chrono,amelmquist/chrono,rserban/chrono,PedroTrujilloV/chrono,hsu/chrono