Reduce verbosity of UM

Richard has found some switches to reduce the verbosity of the UM, which will save time as well.

• -> um
  • -> namelist
    • -> UM Science Settings
      • -> Sections 10 11 12 - Dynamics settings
        • -> Testing
          • -> gcr_diagnostics: 1 -> 0
      • -> Section 13 - Diffusion and Filtering
        • print_step: 1 -> something bigger (they've gone for 4)
        • diag_interval: 1 -> something bigger (they've gone for 4)
        • l_print_wmax: true -> false
        • l_print_theta1: true -> false