Reorg dirs: reorganise `MaterilaItemUtils`
In this MR mainly the source code found in GUI/Views/MaterialEditor/MaterialItemUtils.*
was reworked to disentangle dependencies:
- The non-GUI functions of
MaterialItemUtils
were moved toGUI/Models/MaterialItemUtils.*
- The GUI functions (material related dialogs) were moved to
GUI/Views/MaterialEditor/MaterialEditorUtils.*
- One function to generate a random colour for materials was moved from
GUI/Views/SampleDesigner/DesignerHelper.*
toMaterialItemUtils.*
Edited by t.knopff