Override wfs fix

This is a proposed method to be able to change the WFS_URL from the default. I implemented a test to try and make the old way of doing it work and it is just wrong, so I changed tact to a more normal way to do this sort of thing. Line 38 of pyGDP.py is the real take home. Ignore the big deletion in pyGDP,py, it was an artifact of an old merge conflict... I tried to track things through the rest of the package as well as possible. The test have been changed as needed and I think I tracked passing of the WFS_URL variable to and from the various functions.methods that need it. Review?