remade solve(), non-penetration constraints works ok
few fixes
recompute stuff
moved equation calculation to the individual Constraint
reverse direction of normal in contact equation calculations
angular things
More solve contact fixes, soon angular stuff fixed
angular contributions seem to work
cleanup
support constrained particles
Added frictionconstraint, WIP
cleanup
friction. edited demos to new solver stuff
PointToPointConstraint fixes, WIP
fix point2point constraint a bit
constraint compound: PointToPointConstraint2 with 1 normal and 2 tangent constraint
fixed PointToPointConstraint2
renamed PointToPointConstraint2 to the same but without 2
removed old unused solver code
distanceconstraint ok