ggplot: boxplot(): default colours

Summary:
- Default `fill` color: `white`
- Default `line` color: `grey20`

ggplot2 reference: https://github.com/hadley/ggplot2/blob/4bb9270ef4d5d5062353438fd99d17b6f6de98a2/R/geom-boxplot.r#L231

In Plotly `boxplot()` with default colours:
Before: https://plot.ly/~pdespouy/1989
After: https://plot.ly/~pdespouy/1993

In Plotly `boxplot()` with default colours using `fill=`:
Before: https://plot.ly/~pdespouy/1991
After: https://plot.ly/~pdespouy/1995

Version number will be updated after revisions.

cc// @mkcor