Review BDV todo document

[ehrenfeu]

Check and update what's in TODO-BDV.md.

[ehrenfeu]

@lguerard @CellKai the TODOs listed here should be reviewed and updated during the next coding session:

https://github.com/imcf/python-imcflibs/blob/devel/TODO-BDV.md

[CellKai]

@lguerard @CellKai checked the to-do list and found no open task left