Parameters to be passed on to gmr plotting functions
.gmr_optionsAn object of class list of length 6.
plot_type is the type of plot to create (png is the only option at the mo),
plot_resolution png resolution
plot_size a vector of length 2 containing the width and height of plot (mm)
plot_cols the colour palette used for plotting (recommend the colour-blind palette cbPalette1 or cdPalette2)