[SERVER] Central docker client

[andreaswachs]

What needs to be done?

Different orchestrated resources uses an instance of the docker client to communicate with the docker API.

Since each server only talks to its own local docker instance, it would be easy to put it in a module of its own and be able to fetch it as needed, instead of passing a reference down through submodules.

Acceptance criteria

• Modules are able to get a reference to a docker client instance from a docker comms module