Feature/scenario analysis

this allows scenario analysis by simply calling

scenario_analysis = BackboneScenarioAnalysis(results_directory)
fig = scenario_analysis.plot_system_cost_composition() #just one example
fig.show()

which results in plots like these:

This is still WIP though, since these two dicts in results.py need to be inferred from the input files:

# this default mapping should be changed in the future
default_unitType_mapping = {
    "electrolyzer": "electrolyzer",
    "fuel cell": "fuel cell",
    "rooftop pv": "solar",
    "h2 storage": "h2 storage",
    "resistive heater": "resistive heater",
    "elec import": "import",
    "h2 retrofit": "h2 boiler retrofit",
    "gas boiler": "gas boiler",
    "heatpump_ac": "heatpump_ac",
    "heatpump": "heatpump",
}

# this default mapping should be changed in the future
default_unitSize_mapping = {
    "electrolyzer": 0.001,
    "fuel cell": 0.001,
    "solar": 0.000335,
    "h2 storage": 0.001,
    "h2 boiler retrofit": 0.001,
    "heatpump": 0.001,
    "heatpump_ac": 0.001,
    "undefined": float("nan"),
}

related to #51