Emboss should not span surface faces

[Roger Maitland]

The emboss edge/wire/face algorithm should take the surface face that it's operating on into consideration. Embosses edges should not span multiple faces - recursive division should be used to produce a list of edges, one per face. Embossed wires shouldn't need to change other than accepting a list of embossed edges instead of one. Embossed faces should be modified to generate a list of embossed faces - one for each surface face.

This should result in better embossed results.