* add WireframeMaterial from Qt 3D example
* MaterialSwitcher now has 3 render modes: Solid, Wireframe, Textured
* Remove NodeInstantiator; always create the material and modify entity's components (avoid rendering issues when switching between materials)
* use DiffuseSpecularMaterial for Solid and Textured mode
* create a MaterialSwitcher for all types of meshes (with/without textures)
* add a render settings panel as part of 3D viewport overlay and remove "Textures" entry from outliner
