Big cleaning and refactoring

- Add load_sample_week.run to load a single sample week

- Sample weeks are now independent from the year weeks!
  They have their own directories, their names need not be numbers,
  can be not a ""real"" week but a fictional one (e.g., season avg)

- Add file with week assignments to sample weeks

- Move out 'dummy' parameters from load_year.run to data_year.mod

- Fix subtle bug: close files after reading data

- Add output