Fix plots x axis and stacked look / interactivity

[riccardoporreca]

There are a few problems with the area plots by status. The most relevant ones are in bold.

• [x] The x axis is wrong for both the stacked areaplot and the top-country linepolot , probably shifted

The way we work around the issue with stacked log-scale by plotting the dodged cumulative sum of the data has some unwanted consequences

• [x] Since the areas are transparent, the colors are mixed in => this could be fixed easily with a workaround
• [x] Since the plot is interactive, on mouse over it shows the cumulative sum, not the actual number => must be fixed. Related to this, if one de-selects one of the low series, their area is then shown has belonging to the higher series
• [x] the plot looks pretty heavy, especially since plotly does not do a very good job with the areas since it draws a border around the whole area
• [x] There is still something wrong with the handling of zeros in the log scale, although the issue ~~once we have the active as first plot (can be covered in this issue), although the approach is anyhow not very robust => approach slightly improved, note howeverthe order of the stacked areas was not sensible when always starting with active, and we actually at the present date. A general improvement could be to switching to step plots, see #35

[riccardoporreca]

Switching to a different workaround for the stacked log-scale using geom_ribbon() fixing most of the related problems.

[riccardoporreca]

@fvitalini, you can go ahead in the same feature branch with fixing the x axis and the order of the statuses to "active, recovered, deaths" (bottom to top).

You can also check if the ggplotly() over the lineplots should also have an explicit tooltip argument, also given that the tooltip currently shows e.g. "Status: China"

[fvitalini]

tooltip fixed.

[fvitalini]

@riccardoporreca stacked plot issue not fixed by the right factor order when using geom_ribbon or geom_crossbar but ok when using geom_area

[riccardoporreca]

@riccardoporreca stacked plot issue not fixed by the right factor order when using geom_ribbon or geom_crossbar but ok when using geom_area

This was in fact not a sensible choice, since with the log plots it makes more sense to have closer to the x axis the data with smaller amounts. This logic has been now implemented