remove the type hint FrequencyString

Closes #260

See merge request !362

Remove wavelet function

Closes #254 and #216

See merge request !360

- command line now accespts multiple options `-d`  (data input)
- SaQC can eat now list of Data-like
- SaQC can eat now list of Flags-like
- duplicate columns in input will overwrite former columns (with same name) and we throw a warning see fist thread why this is like this)

closes #257

See merge request !357

Custom optional type for `flag` and `to_mask`

See merge request !358

Revert "Merge branch 'sigcompletions' into 'develop'"

See merge request !359

This reverts merge request !351

Replace `saqc.core.modules` by a pyi-file

Closes #241 and #180

See merge request !351