Mailman2 to Sympa migration scripts (Cernko, Patrick)

This is a fork of Matthias Fechner's mailman2sympa with several enhancements and additions:

• Use ssh to access the Mailman2 list configuration on a different server.
• Added and enhanced Mark Sapiro's mailman-subscribers3.py script to fetch the subscribers with all settings.
• Converted to Python3
• Support for renaming lists and including domain
• Support for as many Mailman2 settings as possible automatically
• Warn about used/modified unsupported Mailman2 settings

The current version of my mailman2sympa can be found here:

• https://gitlab.mpi-klsb.mpg.de/pcernko/mailman2sympa