background is always included as a parameter named "bkgd".
*instfiles* must be ('instr.cfg', 'instr.par').
+ Initial parameters can include parameters named cfg_... and par_...; this
+ will add instrument configuration and parameters to the fitting parameters.
+ They can be given initial values or a None value, in which case the initial
+ value will come from the .cfg or .par file.
+ Use cfg_ALL=1 or par_ALL=1 to add all cfg or par entries to the fit
+ parameters (this is mostly useful to interactively play around with the
+ resolution in one scan).
nsamples = -4 # for plotting: plot only 4x as many points as datapoints