Mixed content

[Madis0]

Options related to mixed content management.

• Upgrade all possible HTTP media in HTTPS sites, block the rest - security.mixed_content.upgrade_display_content = true (or extension)
• Block all HTTP media in HTTPS sites (alternative to option above) - security.mixed_content.block_display_content = true
• Mark sites with unsafe negotiation as mixed content - security.ssl.treat_unsafe_negotiation_as_broken = true

[allo-]

These are interesting for #112 / #114.

I think this needs the option to merge profiles #28, because you do not want to either disable tracking or harden https, but combine both profiles.

I added the "breaks sites" label, as I think this will cause problems with (insecure) sites, even when we do not have an example yet.