Website update before release 14.0

• Remove the publications done with Octopus

• Remove the page https://www.octopus-code.org/documentation/main/octopus_developers/

• Update the developers list https://www.octopus-code.org/documentation/main/manual/about_octopus/

• Add https://www.octopus-code.org/documentation/main/citing_octopus/ to the Manual

• Remove the page https://www.octopus-code.org/documentation/main/manual/deprecated_utilities/

• Add a link to HSCV, Pseudodojo , and SG15 sets in https://www.octopus-code.org/documentation/main/manual/pseudopotentials/. This page also has a wrong {{octopus}}

• Visualization should provide a link to Postopus https://www.octopus-code.org/documentation/main/manual/visualization/

• Update https://www.octopus-code.org/documentation/main/manual/updating_to_a_new_version/

• The link to Xcrysden is not displayed properly here: https://www.octopus-code.org/documentation/main/manual/visualization/