Fix tests for graphs

[cmt2]

Currently we run unit testing on the output of graphing functions by comparing the new output plotting object to a saved archive. This is "fragile" and tests may fail if underlying organization of the plotting object changes despite no change in the graph itself.

In particular, recent changes to scales caused instability to the tests for plotPopSize and we turned off some of the tests for that function.

We need to find better long-term solutions to testing for plotting consistency.