New branch with GLPIClient.py switched from REST to XMLRPC

Hi mcphargus,
so as I couldn't resolve the problem of "not authenticated" messages (same as issue #2), and having a working example of a PHP script using xmlrpclib, I decided to spent some time to try switching your class to XMLRPC. Finally, here it is : and it works now on my installation ;)
I've worked on your code, not fargue59's one, because his was not in git repo. I'm not sure about what his "curried" code provides; maybe it will be interesting to merge it at one time.
I've left your code commented for now. You'll can see that the new code seems lighter : no more need of urllib, nor json (but I let you confirm that last point). I've also added a logout function, and updated some others.
Note that ddurieux and remi, most active developers on GLPI-PROJECT and webservice, admit that the XMLRPC server is more stable than REST one. Remi for example is using exclusively XMLRPC.
I've created a branch, I pull it to you if you want to examine the code.
Thanks for attention.