Silva 1.1 beta1 developer-level changes

Hey developers,

This is an overview of the developer-level changes in Silva 1.1 b1, just 
released. We are not planning any changes for 1.1 final, so this should 
apply to Silva 1.1 final as well. But if we missed anything, please let 
us know! Have fun playing with the new features!

You can find out more about Silva 1.1b1 here:

http://www.infrae.com/news/silva_1_1b1_release

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Developer level changes in Silva
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 From 1.0 to 1.1:

* XSLT support for document renderers. While this shouldn't break
   existing code, it opens up new possibilities for extension
   writers. You can register your own XSLT templates with Silva that
   handle content rendering. Read doc/xslt_renderers_howto.txt for more
   information

* new parser in forms-based editor. The existing parser for bold,
   italic and the like in the forms based editor has been scrapped and
   replaced with a parser that uses a simple HTML subset. The new
   parser should be more predictable for authors and a lot
   faster. Developers who have written their own widgets-based editors
   may need to modify code. If you already use the Silva-1.0
   infrastructure for finding the parser, the changes should be minimal
   and be limited to the UI, however. The Silva-1.0 pattern is::

     supp = context.editorsupport.getMixedContentSupport(model, node)
     supp.parse(text)

* new method on Folder objects, get_public_tree_all().
   Returns a list of all published content objects (including containers)
   below this object (not including this object itself), including
   non-transparent containers like publications.