fix polyface mesh vertices not being applied

[tr3ysmith]

This is to fix Polylines that are polyfaces not getting their indices applied to the vertices.

It also lowers support for polyfaces from R13 to R12. R12 spec supports polyfaces.

[tr3ysmith]

solves #58

[tr3ysmith]

This also adjusts INSERT to allow extrusion direction on R12 as per the R12 Spec:

Table 11-18. Coordinate systems associated with an entity type
+==================================================================+
| Entities                   | Notes                               |
|----------------------------|-------------------------------------|
| Line, Point, 3DFace,       | These entities do not lie in a      |
| 3D Polyline, 3D Vertex,    | particular plane. All points are    |
| 3D Mesh, 3D Mesh vertex    | expressed in World coordinates. Of  |
|                            | these entities, only Lines and      |
|                            | Points can be extruded; their       |
|                            | extrusion direction can differ from |
|                            | the World Z axis                    |
|----------------------------|-------------------------------------|
| Circle, Arc, Solid, Trace, | These entities are planar in        |
| Text, Attrib, Attdef,      | nature. All points are expressed    |
| Shape, Insert, 2D Polyline,| in Entity coordinates. All of these |
| 2D Vertex                  | entities can be extruded; their     |
|                            | extrusion direction can differ from |
|                            | the World Z axis                    |
|----------------------------|-------------------------------------|
| Dimension                  | Some of a Dimension's points are    |
|                            | expressed in WCS, and some in ECS   |
|----------------------------|-------------------------------------|
| Viewport                   | Expressed in World coordinates      |
|----------------------------|-------------------------------------|
| Others                     | The remaining entities have no      |
|                            | point data and their coordinate     |
|                            | systems are therefore irrelevant    |
+------------------------------------------------------------------+

[brettfo]

Thank you for the issue and PR!

The test here will need to be updated. Whether the test is renamed/updated to explicitly allow the extrusion vector on R12 or if it's renamed/updated to ensure it's not present on R11, I have no preference.

[tr3ysmith]

@brettfo Just fixed! Thanks for pointing me in the right direction! Loving this library!