Bevel function for contiguous suite of edges

[jimy-byerley]

This is a function to bevel edges.
It works for a curve (a suite of edges, with no T junction) therefore passed as a [VertexID]
This function is not exactly a chamfer function: a chamfer would cut the mesh leaving the remaining faces in the exactly same position and orientation. The stitch function is already there for this purpose.
This operator is more a way to insert a chamfer-like edge, by displacing points around the edge (the neighboring faces are slightly moved, and not cutted).

I want to add a bevel function for vertices too. I will make an other PR.

[jimy-byerley]

oops, the last two commits are not for bevel_curve but for bevel_vertex that is not mature yet. (I will need something like the Shape::triangulation function for it)

[asny]

Looks interesting! I will take a closer look at it as soon as I have time which might not be until after Christmas, sorry!