Need expanded documentation and tutorials for TabularEditor

`TabularEditor` is a very useful UI component that enables a wide range of capability in a TraitsUI application. The current documentation is limited, and parts of it are presented relative to `TableEditor`, which requires reading and understanding `TableEditor`.
The `TabularEditor` document could be improved by the following:
- Include a range of demos, from a minimal working example, to the currently existing, more fully featured `Tabular_editor_demo.py` and `Tabular_editor_with_context_menu_demo.py.` It would help to include separate examples demonstrating individual features like including images in a row, responding to a change in selected row, and using properties to generate text for the columns. In addition, the existing demos could be reformatted for readability. At least `Tabular_editor_demo.py` is a little hard to navigate because of vertically formatted lists of names.
- `TabularEditor` is important enough that it probably deserves its own separate tutorial.
- Images is the current documentation could be updated to reflect renderings in more-recent OSes. The current MS Windows rendering is looking pretty dated.