Create Line_DouglasPeuker.php

Initial version. As usual, works for our use cases and may not work for yours.

One lame cheat I have in place: The slope/intercept system I use for calculating point distance, won't work on perfectly vertical lines (or those whose coords are rounded off so they run directly north-south) so I fudge an ordinate by 0.000001. Can't imagine this being a significant issue with any realistic map units (light years?).