collision in sublane model when using indirect left turn

[namdre]

the code in MSLink::getLeaderInfo assumes that links with a higher index are to the left of links with a lower index when computing conflicts between connections from the same lane.
An indirect left turn has a higher index but it's geometry is to the right of the straight movers.

(somewhat related to #8500)

[namdre]

might be better solved in netconvert by reordering the link indices so that the indirect left turn comes between right and straight connections.
Probably, we need a new connection attribute to guide the automatic geometry-computation and help with re-ordering.

Maybe a new link-direction code would also be helpful to provide better visualization and help with corner cases in the simulation code.