graphmod: move the graphstyle options to experimental I let this slip in the [ui] section during the review, as far as I understand we don't plan to actually support customisation of the output on we are happy with our choice. The option are just here to help people tests various options so we can decide which one we'll actually use. I'm moving the config option in the experimental section to make this clearer and avoid making them part of the public API by mistake.