Updates for the website

• The page (https://www.octopus-code.org/documentation/main/manual/updating_to_a_new_version/) still write "Octopus 14 (to be released)".
• The license needs update here (https://www.octopus-code.org/documentation/main/manual/copying/)
• We should list the pseudopotential sets provided by Octopus in (https://www.octopus-code.org/documentation/main/manual/pseudopotentials/)
• Building from scratch should contain only cmake
• We should move "Building from scratch" to "Building from scratch (autotools)"
• The link to libxc is broken "https://www.octopus-code.org/documentation/main/" This should point to https://libxc.gitlab.io/
• Broken list at the end of https://www.octopus-code.org/documentation/main/citing_octopus/
• https://www.octopus-code.org/documentation/main/citing_octopus/ also points to the wrong libxc website
• https://www.octopus-code.org/documentation/main/manual/examples/ items are in the wrong order.
• https://www.octopus-code.org/documentation/main/manual/about_octopus/ The "copying appendix" link is broken.