improvements
- auto-upgrade language server to "latest" version (checks once a week)
- use json based meta data to store and check installed server version for faster startups
- directly extract downloaded language server archive to target directory
- remove managed language server if package is uninstalled via Package Control
- manage all logs and session files within managed language server's directory
internal
- optimize code for python 3.8+ (f-strings, type hints, ...)
- auto-format code using python black