Fix plots to compensate for ling legend labels

Currently labels for analyses can be long and make plots unruly. This MR i) places the legend centered above the subplots and ii) removes plt.tight_layout() (this was causing the axis sizes to becomes badly distorted when the label in the legend was long).

Example:

Old plots looked like this

New plots look like this

This seems more organized than forcing new lines at places in the legend depending on the label length.