Python 3 support / Python 2 EOL

It would be good to switch to Python 3 with Python 2 being end-of-lifed.

[PeterSurda]

There is a dedicated developer working on this: https://github.com/jaicis/PyBitmessage/tree/py3porting

Great, thank you!

[yurivict]

@PeterSurda

BM is still not python-3 compatible. The https://github.com/jaicis/PyBitmessage/tree/py3porting repository is also pythin-2.7

Python-2.7 is EOLed and is being removed. The FreeBSD port will be removed too.

[PeterSurda]

@yurivict well the progress is slower than I expected. It will take a while to push all changes upstream and adjust the devops environment. At the moment most unit test work on p3 already.