Remove temporary fix for DEM systems with bilateral constraints.
Remove temporary fix for DEM systems with bilateral constraints.

The code now correctly differentiates between number of contacts and number of unilateral constraints.

Changed to always use an initial guess equal to zero in the iterative solver for velocity corrections.

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