Allow PythonSource var name to be input *and* out
Allow PythonSource var name to be input *and* out

Previously, if using the same name for an input and an output port, the
input would be None instead.

hjanime/VisTrails,VisTrails/VisTrails,hjanime/VisTrails,minesense/VisTrails,hjanime/VisTrails,VisTrails/VisTrails,minesense/VisTrails,VisTrails/VisTrails,minesense/VisTrails,hjanime/VisTrails,minesense/VisTrails,hjanime/VisTrails,minesense/VisTrails,VisTrails/VisTrails,VisTrails/VisTrails