Prepare 0.16.0 release

[veenstrajelmer]

Todo:

• geodataframe_to_PolyFile fails when Polygons are supplied instead of Linestrings #607
• Minor modelbuilder improvements #602
• Add initial fields for tracers #618
• lower xarray/dask to 2022.6.0 when xugrid>0.6.5 is available #582
• convert periodic grid to non-periodic with xugrid #503
• Reduce memory usage of dfmt.generate_bndpli_cutland() #568
• Improve robustness of CMEMS/CDS authentication #603
• set overwrite=False in modelbuilder notebook
• avoid creation of temporary nc files in git folder (temp_*.nc), or delete them after pytest run finishes, or add to .gitignore and maybe in a fixed folder?
• Hide private functions #632
• dsd improvements modelbuilder notebook #631
• While writing .bc file (based on CMEMS-data): skip support points containing NaN's #628
• Add py38 deprecationwarning on dfm_tools import #638

Follow-up: #640