extension mapping for media type and language

[Stephan Koops]

Hi Jerome,

can I start to implement the extension mapping? Or do we need more 
discussion?

I'm not sure to cut the reference or not. We can switch it on by default 
and allow to switch it off.
I will made both Reference variants available in the request.attributes 
map, and also the cut (or not cut) extensions.

FYI: JAX-RS requires to check and remove all extensions (e.g.: URI = 
www.example.com/path/resource.html.abc.en will changed to 
www.example.com/path/resource.abc and Accept: HTML and Accept-Language: en).
I also plan to allow ".html.pdf" and change it to "Accept: 
text/html;q=1,application/odf;q=0.9" and so on.

I have to refactor also the Directory Restlet. I've never used it 
before, so I don't know all capabilities of it. Do the DirectoryTestCase 
tests all of the capabilities?

best regards
  Stephan