append and iteritems are no longer methods of pandas DataFrame.

Failing Tests:

• climada.engine.unsequa.test.test_unsequa.TestCalcCostBenefit.test_calc_sensitivity_pass
• climada.engine.unsequa.test.test_unsequa.TestCalcCostBenefit.test_calc_uncertainty_pass
• climada.engine.unsequa.test.test_unsequa.TestCalcCostBenefit.test_calc_uncertainty_pool_pass
• climada.engine.unsequa.test.test_unsequa.TestCalcImpact.test_calc_sensitivity_morris_pass
• climada.engine.unsequa.test.test_unsequa.TestCalcImpact.test_calc_sensitivity_pass
• climada.engine.unsequa.test.test_unsequa.TestOutput.test_plot_unc_imp
• climada.engine.unsequa.test.test_unsequa.TestOutput.test_save_load_pass
• climada.util.test.test_lines_polys_handler.TestGeomImpactCalcs.test_calc_geom_impact_mixed
• climada.util.test.test_lines_polys_handler.TestGeomImpactCalcs.test_impact_pnt_agg