removed deprecated functions on spectral datastructures

*  rebin_like(a, b0) / rebinLike(a, b0)
-> were just (two identical?!) shorthand forms of
     b.value = rebin(a.bin_lo, a.bin_hi,   b0.bin_lo, b0.bin_hi, b0.value);
   WITH WRONG ERROR PROPAGATION

*  fits_save_model
-> did a fits_write_binary_table with the model evaluated on a fine grid

*  selectData / selectData_en
-> were from a time when I didn't know the struct_filter / _A functions...