The patch includes following improvements:
- handleAfterKeyPressEvent was only used to adjust margins. We don't do it anymore, so get rid of it.
- Add support for Tab key to increase indentation level (either at the beginning of a list item or with multiple lines selected)
- Fix canIndent / canDedent logic when cursor has a selection. canIndent should work with topOfSelection, and canDedent --- with bottomOfSelection.
- Enclose handleOnIndentMore / Less in beginEditBlock / endEditBlock, so they appear as a single event in Undo stack.
- A Return on an empty list element decreases the indentation (so double-Return terminates the list)