Website updates

[giovannipizzi]

• Update logos of institutions: add PSI, update old logos e.g. Imperial, possibly add links to each of them? @mostofi
• Check package-manager availability: Add "Install via package manager" line on Download for the supported ones: Fedora, coda-forge, ... @JeromeCCP9
• Remove old FORD docs now hosted on GitHub pages, add redirect @giovannipizzi
• Update references to tutorial solutions to the new online docs once Addition of Tutorial solutions to the online documentation (old solution booklet) #692 is merged @giovannipizzi (at least 2 places)