Add new figure to show selectivity deviations

[aaronmberger-nwfsc]

From internal reviewer comment for future work:

[Wishlist for the future: these figures [time varying selectivity plots) don't make it easy to understand the parameter deviations, so consider adding yet another selectivity figure if you're going to discuss selectivity deviations in the text.]

This is in reference to text that talks about certain years and ages where deviations are particularly different or whatever.