Help with WICKET-6028

[andrea del bene]

Hi everybody,

lately I had quite a time trying  to fix WICKET-6028. In short, the 
problem is the following. When we have markup inheritance two components 
(two TransparentWebMarkupContainer) are associated to tags 
<wicket:child/> and <wicket:extend>. Since they are MarkupContainers, 
these two components perform auto-components dequeueing when they are 
initialized. However their corresponding tags are skipped during 
dequeuing process (see MarkupContainer#canDequeueTag) leading to the 
problem of this issue.
I've tried different approaches to find a solution (allowing tag 
dequeuing, changing TransparentWebMarkupContainer queuing logic, etc...) 
but I always ended up breaking some (markup) parsing rule of the 
framework. The only approach that seems to work is to treat tags 
<wicket:child/> and <wicket:extend> as raw tags, without associating any 
component to them. I've attached this fix to the issue.

Let me know if you have better ideas or any other kind of insight about 
this problem (or if you absolutely dislike my proposed fix :-) ).

Andrea.