HSAF SMDAS SWI

[wpreimes]

Do you want to include the SMDAS data reader in this package? https://github.com/wpreimes/ascat/blob/smdas_reader/src/ascat/smdas.py

Then I'll fix some issues, clean up, write tests etc for it.

The data itself is a bit awkward, corrupt files, missing variables, deviating time stamps in metadata and filename etc. Therefore the reader is also a bit messy...