[com4], [ana5]: Add Flowpy thalweg postprocessing

[PaulaSp3]

• Add Scripts for 2D plots
• Add scripts for statistic plots
• try to use mostly Avaframe functions (e.g., for plots)
• use ini file for parameters and the path
• Add docu
• make 2d plot for every pickle in thalwegdata folder?
• mark functions that are not used currently

[PaulaSp3]

-> statistic plots are in OpenNHM/AvalancheTerrainIdentification -> mod3Map/regionalThalwegAnalysis.py