Update DDL

[veenstrajelmer]

Todo hatyan/ddlpy

• move ddl to geopandas dataframes where possible #200
• support for newer pandas versions ddlpy#20
• update ddl example script to ddlpy #201
• avoid invalid rows in measurements dataframes ddlpy#29
• add check for nodata for entire period instead of retrieving all periods ddlpy#26
• simplify ddlpy_to_hatyan and assume already-flattened QC array #203
• add sorting of returned timeseries ddlpy#27
• Make duplicate dropping optional ddlpy#24
• Add support for time strings in ddlpy.measurements() ddlpy#39
• add function to simplify measurements dataframe ddlpy#42
• Improvements for measurements dataframe ddlpy#38
• Add distinction between waterlevels and extremes with "Groepering.Code" ddlpy#21
• ddlpy: add more features from getonlinedata.py
• add ddlpy dependency and enable testcases #207

Follow up issue in kenmerkendewaarden repository: Deltares-research/kenmerkendewaarden#4

[veenstrajelmer]

This issue can be closed since all issues are ddl/data related. Haytan does not have ddl functions anymore, since it uses ddlpy now. Also, the data related issues are mainly relevant for the kenmerkende waarden project, so these are moved to Follow up issue in kenmerkendewaarden repository: Deltares-research/kenmerkendewaarden#4