Added some new fancy config options

[HofiOne]

• Option enable_copy_code_button to add copy button to Code blocks
• Option page_content_width to set the width of the inner content part of pages
• Option sidebar:sticky to be able to stick the navigator left sidebar to the the top
• Option masthead:sticky to be able to stick the navigator top bar to the the top
• Option masthead:hide_navigator to be able to hide the navigator item of the top bar

At code level, added possibility to define separate width values to the left sidebar

Signed-off-by: Hofi [email protected]

[iBug]

This could certainly be useful, but it's too large and a bit messy to review. If you split each feature into a separate PR, I'll look more favorably on this.