Allow set shading mode per view, per camera, etc.

[u2fly]

Is your feature request related to a problem? Please describe. LeoCAD allows to set projection type per view, but there is no way to set shading mode per view.

Describe the solution you'd like

LeoCAD should allow to set shading mode separately:

• per view;
• per camera in scene;
• for part "Preview" widget;
• for parts peview in "Parts" list widget.

Describe alternatives you've considered None.

Additional context

[u2fly]

@leozide, I created this issue without template, so to clarify, this is a "Feature request".