Use data labels for axis labels by default

[sethaxen]

When using Data and passing property names, it would be convenient if StatsMakie defaulted to using those property names for the corresponding axis labels if the user has not already set the axis labels. Here's an example:

using Makie, StatsMakie, RDatasets
mtcars = RDatasets.dataset("datasets", "mtcars")
p = violin(Data(mtcars), :VS, :MPG)

What we get:

What I would like to get:

[piever]

This is definitely planned functionality. The problem right now is that StatsMakie is mostly implemented with the convert_arguments functionality that converts arguments into list of plot types, with converted arguments and new attributes. The problem is that the axis labels belong to scene[Axis] so are not readily acceptable here. We should probably discuss at VizCon what is the correct implementation.