Have librdf open the urls in load_into_model instead of using python

Have librdf open the urls in load_into_model instead of using python
As a side effect I ended up discovering that my parser type detection
code for file types was wrong, and now it has test code

I was trying to fix a bug where librdf 1.0.10.1-1.1ubuntu1 was
segfaulting when loading into the model but I couldn't figure
out what was doing it.