Move minify setting into expandable area, and warn

[bobrippling]

This moves the minify option to an expandable advanced section, and changes the warning ("may" -> "will"). See #2562 for more details.

Deployed to my gh pages if you want a preview.

[gfwilliams]

Thanks! Looks good, but maybe you could move the 'translations' setting above the 'Advanced Options'? it's a bit odd having it in the middle.

Also, I really appreciate the link for testing - it makes life so much easier!

[bobrippling]

Yeah that looks much nicer - gh pages updated too if you wanted to re-check (maybe a bit of a gap (<br>?) between "advanced options" and the "default settings" button?)

[gfwilliams]

Looks great, thanks! Actually I think I'll move the 'Default Settings' button into 'Advanced' then it's less likely to get accidentally clicked!

[bobrippling]

Ah nice idea, and thanks for merging!