New feature: remove center vertex

[PJK136]

Description

Add a new topological operation to remove a vertex and its incident halfedges by merging all incident faces.

In other words, it's the reverse operation of void split(Face f, Vertex v);

Motivation

Share the implementation with the upstream.

Benefits

To have void split(Face f, Vertex v); and its reverse operation.

Drawbacks

None.

Applicable Issues

None.

[dsieger]

Hi Paul, thanks for your submission. Just gave it a try, and observed two issues:

1. The function seems to only work on triangle meshes. It crashes on quad / polygon meshes. You can try with the fandisk_quad.off model from the pmp-data repository or any triangle mesh converted into a polygon mesh using the dual() function.
2. The function does not handle boundary vertices, which makes sense I guess. However, it should be documented as a pre-condition of the function. A corresponding assert() or even an InvalidInputException would be helpful as well.

Thanks,
Daniel