Support nested expand macro

Currently the bundled expand macro doesn't work well when it's being used nested as something like this:

• http://ffeathers.wordpress.com/2011/08/20/nested-expand-macros-in-confluence-wiki/

A sample of this page has been created here at http://sandbox.onconfluence.com/display/FWDOCS/Test+Nested+Expand+macro

Quoting one of a user's explanation on how it doesn't work properly:

#	Test Steps	Result
1	Click on '1st... Click here to expand'	2nd and 3rd expandable areas are expanded which feels to be incorrect behavior. Arrows are directed incorrectly two. First arrow points down which means expanded area, however second and third arrows point to the right but the areas are still expanded.
2	Click on '3rd.. Click here to expand...'	Expanded area collapses and the arrow changes direction too, so the direction is wrong again
3	Click on '1st.. Click here to expand...'	3rd expandable area expands instead of collapsing the whole area

I can continue the list.
I think the problems above are enough to say that the functionality of having expandable area in expanded section is not working properly.

Workaround

Create expand1, expand2, expand3, etc as a separate macro as described here. Use the user macro instead of the bundled expand macro. It's copying the suggestion at this blog post.