Change out the simplification algorithm

[gdey]

We should implement and try the simplification algo described by (https://bost.ocks.org/mike/simplify/). This algo has the potential to generate better shapes for us.

[hcliff]

I've got some code for this, it needs to be ported over to using an rtree for perf reasons, but it's got cooked in logic to avoid self-intersections, will tidy up and throw over the fence