Update NOC NPD docs

[oj-tooth]

Routine Update of NOC Near-Present Day Documentation:

• Update Outputs page to include reference to NOC STAC browser on OceanDataStore website.
• Update diagrams of JASMIN OS organisation.
• Add details of NEMO MEDUSA simulations.
• Add change log page with updates - include new releases, updates to ongoing simulations etc.
• Update information on diagnostics.
• Update validation for NOC NPD physics-only.