Improve tractive force & wheelslip calculation

Improve tractive force and wheelslip calculation, by adding "OrtsDriveWheelWeight" param to diesels and electrics so the simulation of driven/non driven axles are possible, later the visuals should be improved too, ability to set which axles are driven, and which are not, so the wheelslip rotation only applied on driven axles.
Perhaps if possible, fix the oscillations in the curtius-kniffler method.

Discussion: http://www.elvastower.com/forums/index.php?/topic/28534-advanced-adhesion-and-wheelslip/page__view__findpost__p__204085
Roadmap: https://trello.com/c/2ESRCVsA/329-improve-tractive-force-wheelslip-calculation