change escape plots (version 2.0)

[jbloom]

This updates to version 2.0, by making some backward-incompatible changes to how the escape plotting is done. Now the lineplots and heatmaps are on the same plot, the code is more general, the filtering on mutations is updated on site plots, and some other problems (like this one are fixed.

This pull request also enables code using this plotting to be augmented to address the following issues:

• allowing functional data to be visualized and filtered on in escape plots
• better scaling of heatmaps when negative or positive values are very small in magnitude