sippi_plot_defaults: Sets default options for ploting (such as fontsize)
 
  Call :
    options==sippi_plot_defaults(options);
 
    % ALWAYS USE DEFULT SETTING (overrules options.axis)
    overrule=1; % {default overrule=0)
    options==sippi_plot_defaults(options,overrule);
 
  See also: sippi_plot_posterior, sippi_plot_posterior_2d_marg