import error for modules and methods in fdf/modules

I added `<method name='fft'></method>` in bes.xml in branch drsmith.  If fft.py is in fdf/ or fdf/modules/bes/, then bes.ch01.fft() is callable.  If fft.py is in fdf/modules/, then bes.ch01.fft() throws an import error.  I think modules and methods in fdf/modules/ should be callable.  (Alternatively, am I adding fft() improperly?)
