output triples in debug mode

[simeonvandersteen]

• Triples to be stored, in case of PUT
• Triples fetched, in case of GET

using something like librdf_model_print (although that specific one is deprecated)

[simeonvandersteen]

Replacing the debug function in curl could also work (http://curl.haxx.se/libcurl/c/CURLOPT_DEBUGFUNCTION.html)