WIP: improvements and simplification of python and docker packaging

[olivierkeke]

This PR improves python and docker packaging:

• Rename the package enoceanmqtt in HA_enoceanmqtt to avoid conflicts with enocean-mqtt library.
• Remove useless copy of enocean-mqtt modules.
• Create a separate main module to replace patched main function of enocean-mqtt.
• Move Dockerfile at the root of the repository so that python sources are in the build context.
• Copy directly python sources in the docker image.

I've pushed a working docker image on dockerhub: docker pull hollysaiqs/ha_enoceanmqtt:latest

Please notice that standalone installation files must also be modified.