The explicit activation of the MaterialWorkbench breaks the toolbars layout for every start. When fixing it manually it will be broken
again after the next start.
Because the core doesn't depend on the Material module it's a no-go to add an explicit runtime dependency to the corresponding workbench.
Since the Part module depends on the Materials module and the PartGui on MatGui the correct way is to let Part an PartGui load their
dependencies.
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.
