Trajectory Planning in `compas_fab`

Hi, probably it is not a bug but does happen several times when using compas_fab, and can be a potential update for a better user experience.

When using robot.plan_motion in Python or the ‘Plan Motion’ component in Grasshopper, the output trajectory varies in terms of path rationality. Certainly, multiple trajectory solutions are caused by a lack of constraints and we can find the ideal trajectory solution by clicking ‘compute’ multiple times, but it would be great if this function can auto-rank or auto-provide the best output, i.e. the shortest travelling path.