WIP: allow to use arguments in default theme

[piever]

The default_theme function now also gets passed the converted arguments, which allows to customize the theme as a function of the arguments the user is passing , for example:

density(Surface, rand(100,2))

could be instructed to use Surface theme.

[piever]

I'm not particularly convinced by the implementation of the PR, but I hope it illustrates the idea (as a side effect, it causes the axis frame to disappear, not sure why).

This is an example of how it could be used, so that:

density(rand(100))
density(rand(100, 2))
density(Surface, rand(100, 2))

use themes from Lines, Heatmap and Surface respectively.

[piever]

For it to be non-breaking the function passed to the macro discards the keyword arguments by default, but maybe there's a smarter way to avoid having to write the function twice.

[piever]

Closing as after the StatsMakie redesign as well as #46 this doesn't seem relevant anymore.