Figure improvements 4/x - Contributions graphs with negative values

[marc-vdm]

The contribution (elementary and contribution) graphs could be improved by showing totals in addition to the other values already present. This is primarily the case when negative values are present like in the figure below. An indicator line or something else that shows the total would help users identify absolute total impact vs total negative and total positive impacts.

In addition to this, when considering relative results, the graph and table should be negative as well. The current implementation is shown below as an example. It would be ideal if in this case, the graph was

1. flipped (from -1.28 to +0.28)
2. the total was shown (at -1)

The red line indication is just an example, another way of indicating the total should also work

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edit: Also, these axis numbers don't make sense at all.

[marc-vdm]

See also Figure 3 in Zink et al. (2014) for an example of this.