tight_layout fails in multipage_plot_iterator when page not full

[cpbl]

I think we should make hidden axes in the rest of the axis locations, in order that the caller can call layout_tight after the last subplot is plotted.

[cpbl]

After trying many things, including changing the page size according to how many rows are used, I gave up and asked for help:

http://stackoverflow.com/questions/44059159/use-of-tight-layout-in-matplotlib-with-incomplete-axis-array