Option not to print plots, but to return the plot object

[jmberros]

It would be useful to have an option to return ggplot objects instead of printing them, in the plot methods. This would allow to arrange the plots in a custom layout using grid.Extra or to modify some of the plot elements before printing them.

For instance ols_plot_resid_qq could end in a return (p) instead of a plot(p).

Or ols_plot_resid_lev, is printing and returning the plot in a list:

I would add an option that defaults to TRUE, print_plot = T to every plot method, so that the current behavior is not altered. What do you think?

[aravindhebbali]

Thanks for the suggestion @jmberros . Will do this in the upcoming release.