Move snapping to terrain and line subdivision to modifiers

[brnkhy]

Again started this with #23 and implemented the basics at cuttingHoles branch

Implemented these as mesh modifiers. Second one is named "SmoothLine" for now though and that's a horrible name. I guess I'll change that to "IncreaseDataResolution" or something. that line subdivision should be done before terrain snapping though, it's not obvious or checked/forced at the moment.

you can see the effect of subdivision below;


That would look even better as terrain resolution increases as well.

[brnkhy]

done in #53