Create 2D Grace plots of the exponential curves.
file: The name of the file.
dir: The directory name.
force: A flag which, if set to True, will cause the file to be overwritten.
norm: A flag which, if set to True, will cause all graphs to be normalised to a starting value of 1. This is for the normalisation of series type data.
This is used to create 2D Grace plots of the individual exponential curves used to find the R2eff or R1rho values. This supplements the grace.write user function which is not capable of generating these curves in a reasonable format.