Omc session zmq docker2 (#306)

* [OMCProcessDocker] improve handling of docker_cid

* [OMCProcessDocker*] cleanup user handling - variable current_user not needed anymore

* [OMCProcessDocker*] rework inheritance chain; no multiple inheritance!

* [OMCProcessDocker*] reworked inheritance chain - use change for _omc_process_docker()

* [OMCProcessDocker*] reworked inheritance chain - move _omc_port_get() to OMCProcessDockerHelper

* [OMCProcessDocker*] rename class methods

* [OMCProcessDocker*] move content to OMCProcessDockerHelper

* [OMCProcessDocker*] rename class methods (2)

* [OMCProcessDockerHelper] fix _docker_process_get() - definition of docker_cid

Author: syntron