First implementation of GF profiling files collector.

If profiling is enabled.
This commit introduces the version 0.1 of the app to crete rdf/xml from django models.

More information are available into the app code documentation.
Updated version 0.1 of the app to crete rdf/xml with some changes on utils and urls.
Update: add Product proxy model

Now the view showing the catalogs contains Product objects in addition to Supplier objects and SupplierStock objects
Merge branch 'matteo-dev' of https://github.com/feroda/gasistafelice into matteo-dev

Conflicts:
	gasistafelice/rdf_gf/proxies.py
	gasistafelice/rdf_gf/proxy_models.py
	gasistafelice/rdf_gf/rdfxmlutils.py
	gasistafelice/rdf_gf/views.py