Extend modular blueprint to add header.onpage_menu

[flaviocopes]

No description provided.

[olivierdalang]

Heh that was quick. I just tested, it works, but :

• it writes onpage_menu: '0' or onpage_menu: '1' to the file. I guess onpage_menu: false / onpage_menu: true would be cleaner
• it takes two actions to change the default behaviour (which is to display the single page menu) : you must activate the option, and set it to "disabled", which is a bit counter intuitive I guess. Is it possible to have the default to "disabled" so that you just need to activate the option ?

Thanks for super-fast support :)