[Bf-python] Mesh.Face() constructor

[Ken Hughes]

Somebody (maybe Hos?) on IRC today was asking why there is no 
Mesh.Face.New() constructor function in the Mesh API.  I just wanted to 
tell whoever that was that I'd like to add one, but can't seem to get a 
consensus from users as to how to implement it.

The specific problem isn't the constructor itself, but how to 
efficiently add faces to a mesh.  I'd personally like to just add faces 
to the mesh and have the API insert the necessary vertices, but brings 
into question how to avoid -- or allow -- duplicate vertices while doing 
  so.  Otherwise it could work as NMesh.Face does and require the verts 
to be created first.

Ken