Make library work with FGW14-USB communication

[michaelpiron]

This pull requests makes the library work with communications over the FGW14-USB gateway.

A refactoring of the code was done by @JBosecker (thanks for your contribution).
Changes:

• Removed functions for locking, unlocking, creating devices etc. , as not possible with the FGW14.
  The functions were used to communicate on the Eltako bus via USB on the FAM14, but this was not a use case that Eltako designed for. Just an example: If you lock the bus and unlock it again, all current states of the actors are dismissed (like the current scene for FSB14).
• CoAP: not sure these functions were working, and these were not fundamentally needed for the library to function.
• Added message types, because they were needed for the communication (1BS).
• "device" elements not necessary anymore.
• Reimplemented the EEP functions to interpret and create messages based on the official EnOcean documentation and other implementation (e.g. FHEM).

[michaelpiron]

Dear @JBosecker,
thanks for your effort to improve this eltakobus Python library.

I'm trying to understand the code changes you made and why you made them.
Could you enlighten me by briefly describing here what you changed and why?

I saw for example that the CoAP protocol support is dropped, that the bus locking/unlocking is out. But there are other changes as well, and I'd like to understand why.
Based on your answers I can update the README as well.

[JBosecker]

Hey @michaelpiron
I'm so sorry for the late response. I didn't get any notifications about the progress...

I tried to get this library flying with the FGW14.
All the stuff like locking, unlocking, creating devices etc. is not possible with the FGW14 (in my opinion).
Just the FAM14 connection via USB would allow this kind of stuff.
But I think this is not how it was designed by Eltako.
Just an example: If you lock the bus and unlock it again, all current states of the actors are dismissed (like the current scene for FSB14).

For CoAP: I'm not sure if this was ever working and also if this is needed in this library.

I also added some message types, because they were needed for the communication (1BS).
The whole device stuff was not necessary anymore, so I threw it away.
Additionally I reimplemented the EEP stuff to interpret and create messages based on the official EnOcean documentation and other implementation (e.g. FHEM).

I hope that's enough as an explanation.
If you have further questions, please don't mind asking.