changed continuous version of planarity to change from energy 1 to energy 0.5 (instead of energy 0). This way, a completely resolved crossing is better than one where one of the nodes still intersects with the other edge.
Applied to both regular and approximated planarity measures
Modified attraction and repulsion measures: Attraction is now really only attraction (instead of deviation from ideal length, which comprises both attraction and repulsion).
added scalefactor (to both attraction and repulsion). Davidson harel's formula expects all points to lie within a unit square. This is not the case in OGDF, so distances are scaled to approximate this situation.
Squaring of attraction energy makes more sense with the scaling: it is a weaker constraint, allowing more room for finding a planar layout.
implemented plotting of energy and temperature as a function of time