Cleanup defaults

This merge does a couple of things:
- cleanup the remaining references to obsolete arguments (template,
   modelname, etc.), and to old docstring/comments.
- fixes the default values of `runpyFBU.py`, which was broken after the
  `data` dir reorganization. It is now working again "out of the box" as
  > python/runpyFBU.py
- remove the un-necessary empty lines, and simplify some loops
- allow for no background
Please let me know if it runs fine for you.