Add command line option --route-reuse to override the default setting of
10 to experiment with better route reuse settings

Adjust the TradeCalculation distance weights to give a better result.

Adjust some of the sort vs sorted uses for cleaner code. 

Increase the number of worlds left in the stars list used for
determining routes. It was too restrictive and was removing too may
links. May need more exact system for sorting to get better results.
Update HexMap to latest version/API of PyPDFLite.
Tweak the distance_weight value used for determining weight of trade
over distances. Add several variations based upon discussions on CotI.
Add documentation for the route-reuse command line option.