多段线简化

https://github.com/omarestrella/simplify.py

https://www.npmjs.com/package/line-simplify-rdp

https://www.jasondavies.com/simplify/

https://bost.ocks.org/mike/simplify/

http://desktop.arcgis.com/zh-cn/arcmap/10.3/tools/cartography-toolbox/simplify-line.htm