Integration tests with both Python 3.7 and Python 3.8

• Updated some requirements so that dtcontrol works with Python 3.8 as well.
• Started using ubuntu:rolling instead of alpine as the base image so that installation of the requirements becomes simpler.
• Renamed name of the package to dtcontrol from dtcontrol-tum previously, also bumped up version to 2.0.0dev1 because of Mathias' new work.