Add page-specific settings to sidebar

[mob8607]

It would be nice if we have a separate place where we could add page specific settings. Currently we have several different solutions for this (sometimes directly in the page, sometimes we have toggles somewhere on the side of the window)
It should be directly visible, that a page has some specific settings.

Example:

• In some projects we have specific items in a cart which we want to disable in the styleguide.
• We have a forms page and an input field to select the wanted form.