Release 0.4.4

If you are currently using label studio pip package, please upgrade to
pip install -U --force-reinstall label-studio==0.4.4.post2

New features

• Export to multiple formats on "Export" page depending on chosen label config
• Onboarding setup for new project
• Run label-studio start-multi-session to enable session persistent mode: Label Studio creates new project per each browser session
• On-the-fly label config validation: now you can safely change label config in the middle of the labeling process (i.e., adding new labels)
• Deleting tasks through UI

Misc

• Support for python>=3.5 and Windows
• Updated and published docker image
• Generating sample tasks fixes