xmlcheck plugin

Hi Daniel,
I updated and installed kdeaddonw/kate to get your new plugin.

First, I think this is a nice tool, and it seems to do what it should.

Then some comments:

1) "Validate XML" is not editing. Preferably a tool like this should go in the 
"Tools" menu, or a file type specific menu, in this case obviously "XML".   
  That actually makes me repeat what we discussed before, namely that the XML 
plugin imho should put it's actions under menu "XML" as well. It would add 
logic and help having less cluttered menus. 
  If you change the "XML plugin"
menu to just "XML", and have the checker add a separator and a "Validate" 
action, all would make great sense.

2) For some reason the contents of the listview wouldn't show up untill I 
hide/showed the view - which btw should have a better name than "test" :)
  Try calling show() on the widget you pass to kdockwindow::setwidget()

3) for this as well as the XML plugin, they should be hidden unless related to 
the current file. I have a perl toolkit coming up adding a "Perl" menu, there 
is allready a plugin adding a "Python" menu, and I guess we are looking at a 
growing number of file type specific plugins/tools.
  I don't think you should do anything about that, except agree that it should 
be done. I plan to add the ability to the plugin manager of hiding/showing 
plugin GUIs based on file/mimetype/hl filters.

-anders