Add :x-axis, :y-axis to all charts

I'd like to discuss how to add options for x, y axes to all charts [where it makes sense].

I have a few challenges I'd appreciate an advice on:

1. Where does it make sense to do this for all applicable chart? So far I have blindly added a call to `set-axes` to wherver call to `set-theme` was
2. How to test that it works? Do we f.ex. have a file that creates all the possible charts and has, for each one, display what they should look like? I feel that it would be quitedifficult for me to 1) find out how to create all the charts (yeah, go through docs, copy the simplest example, ...); 2) check that they look reasonably (perhaps w/o and w/ a custom axis / axes?)
3. It likely does not work for all charts;they either must have range + domain axes or 
    1. be a PolarPlot - which hasn't x, y axis but just one axis, so perhaps the default keys `:(x|y)-axis` are confusing? how to handle these special cases nicely?
    2. be a ThermometerPlot - only one axis as on PolarPlot, called range axis
=> what to do for the other charts?

I'd also appreciate recommendations regarding improvements of the code.

PS: **the tests are broken now, I'll fix them eventually**