Convex hull operator

The initial form created around branch nodes in the skin modifier is a convex hull. I think there are some useful cases for convex hull outside of the skin modifier, so I’ve split this code off into a new BMesh operator and added a corresponding user-accessible operator. The gif above shows an example of how a convex hull can be used as a bridge tool between faces (Blender’s current bridge tool only works if the faces have an equal number of vertices.)

I’ve pushed the code to a new github branch, it’s also in the code review tool.