Resolve "add PicoTech pt104 data logger"

Closes #81 (closed)

@pyBear0511

• figure out how to mock software tests (demo mode? cf. TiePie library mock approach) decided to skipped for now
• write software tests only quick pure-python tests: instantiation, config validation, ... (anything else?)
• add example script

@mikolajr @pukhlyakova

• if Linux package is brought back: https://www.picotech.com/support/topic40626.html; [update, 9 Dec 2020] try .deb files found in https://labs.picotech.com/debian/pool/main/libu/libusbpt104/
  • add lib to CI
  • add lib to devel Dockefile
    • try w/ a workaround for udev restart if this is not resolved beforehand: https://www.picotech.com/support/topic40771.html
• add OS check for import in dev/__init__.py (Windows-only if Linux is not working, otherwise both)
• add picotech extras_require in setup.py
• update features list (authors done in Lauda MR)