Column order and index when stacking/unstacking

[jnnr]

• For stacking/unstacking to be reversible, the columns have been sorted. This is not ideal. The index order could be retained when unstacking. However, if some other step is performed with the stacked data, that information would be lost.
• This has consequences even here!:

  oemoflex/oemoflex/model/model_structure.py

  Lines 313 to 316 in 3431118

  	# sort the columns for comparability
  	component_df = pd.DataFrame(comp_data).set_index("name")
  	component_df = component_df[sorted(component_df.columns)]

• There is no guarantee that the index of the dataframes is always the same. When load from_csv_dir, DataFramePackage assumes index_col=0.
• This is connected to

  oemoflex/oemoflex/model/datapackage.py

  Lines 494 to 495 in ad39494

  	# TODO: Check if this step is necessary only because function is used differently in some cases.
  	_stacked_frame = stacked_frame.reset_index()