visualisation / statistics for second manuscript (MR !17)

• issue:
  • create figures and statistics for 2nd manuscript
  • improve input and output data
• solution:
  • improve the combination of nutrient and flux data
  • for many visualisation and statistical analyses, a new function was created or an existing file adapted, e.g.
    • create_temperature_response_function.R to see the temperature response in the chamber (not used in the end)
    • visualise_RF_pdp: code for doing RandomForest analyses and compute PartialDependencyPlots
• testing:
  • run_all_main.R: works to calculate GHG fluxes (with still some bugs that weren't fixed with MR !11 (merged) .
  • code works for most visualisation of 2nd manuscript (L-D differences, CO2, hotspot) and stats (RF - ANOVA still needs to be done)

Closes #30 (closed)