Implement OCPP 1.6 Security

[juherr]

@florinmandache I built on your work and made the minimal required changes.
Some tests would be very welcome. I also noticed that CSMS security requests aren’t implemented yet.

@goekay It seems to be working (at least it starts correctly), but I haven’t fully tested it yet and it could use some polishing.
Feel free to rework or improve it as you see fit.

Fix #100

[goekay]

@juherr i will take a look at this ASAP when i am finished with some other duties.

on a more general note: i had a conversation with @florinmandache after his initial big PR. he said that he has many things going on and is short on time, and he wanted to contribute on good will. since he is a busy person, he was not interested in follow-up, review rounds and eventual clean-ups (i.e. the usual process of PR and reviewing). due to the substantial nature of the contribution, i accepted it as-is and took it upon me to do whatever is necessary to bring these features to main branch.

in this context, i thank you for doing one part of it.

[juherr]

@goekay Thanks for the clarification. I think Gemini did an interesting initial job exploring the different topics, but it definitely needs more work based on what I’ve seen so far (especially regarding OCPP 1.6 Security and OICP). Since OCPI and OCPP 2.x are an even tougher challenge, and my time is just as limited, I’ll let you take the first shot on those ones 😉