Context Navigation

Changes between Initial Version and Version 1 of Ticket #4933

initial	v1
1	1	You can focus a MenuSeparator and a ToolbarSeparator and should not be allowed to. This is because these widgets get assigned a tabindex=-1 when added to the menu and toolbar. Did a quick fix for 1.0 to prevent an error (see #4927) but need to create a more complete solution.
2	2
3		The problem can be seen if you focus a toolbar button, then click on a toolbar separator that is not close to the button. The separator gets focus and the previously focused button loses focus indication. If you then press a right arrow key, focus will go to the button that was next to the previously focused button.
	3	The problem can be seen if you focus a toolbar button, then click on a toolbar separator that is not close to the button. The separator gets focus and the previously focused button loses focus indication. If you then press a right arrow key, focus will go to the button that was next to the previously focused button. Which is what we want but is visually odd.
4	4
5	5	The same problem occurs in the context menu but is not as evident since the menu item which was focused before the separator is clicked still "looks" focused.