Uses new material system for appearance
Each feature object now has a property called ShapeMaterial that
describes its physical properties. If it has a shape, it has a
material.
The ShapeColor attribute is replaced by a ShapeAppearance attribute.
This is a material list that describes all appearance properties, not
just diffuse color. As a list in can be used for all elements of a
shape, such as edges and faces.
A new widget is provided to allow the user to select materials in a
consistent fashion. It can also launch the material editor with its
more advanced capabilities.
These are the bare minimum set of APIs for future new topogical naming
feature (see [here](https://git.io/fj6hy) for a overview of the new
APIs).
These APIs are added early to avoid too much code change for the new
features introduced in the current patch set.
fix inheritance of MeshFeaturePy
fix inheritance of PartFeaturePy
remove useless test() method
implement getPyObject in GeoFeature in case a sub-class doesn't implement it
