ENH: Use subject hierarchy in Models module
- Only shows model and model hierarchy nodes (which are represented as SH folders)
- All plugins are disabled except for Models, Folder, Opacity (and Default)
- Apply color to branch action provided by the Folder plugin replaces the checkbox in model hierarchy
- When the user changes the color of the folder then this option gets enabled automatically
- Can be enabled/disabled using a checkable visibility action (right-click on eye icon or color)
- If enabled, then visibility only applies to the folder, otherwise the default SH behavior is used (show/hide all items in whole branch)