Better parameter read function

Deprecating get_params_from_file because it was using load_par.
Several problems arise from this:
  1) Requires the parameter file to be loadable, i.e, the functions
     used in the parameter file must exist.
  2) Possible interference with currently loaded parameter values
     especially with tied functions.
  3) Assigned functions to datasets show up in the parameters, but
     are not visible in the function string.

To overcome this, a simple parsing is done, returning the available
information similar to get_pararms. A drawback is, that the model
dependend paramter settings (hard_min/max,step,relstep) are not
available from the parameter file (they have not been before, but
assuming the functions was the same, they effectively have been).