Support remote Docker

[madoar]

As far as I understand the code, winebuild currently requires docker to be installed alongside it to function correctly.

This may not be the case on every system.
Therefore, I think we should use a config file to specify the location of the docker service used by winebuild.

[qparis]

Why not directly install winebuild alongside with the system that has docker?

[madoar]

I'm not saying that you mustn't do that, I just describe the possibility that someone dosn't want to install winebuild on the same system on which docker is installed.
A possible reason could be, that you have a dedicated server only for executing docker containers.

When reading my own issue I understand that I forgot to add some additional context:
In addition to making the location of the docker service configurable, I also want to recommend using a python library to communicate with docker instead of a process builder.
This would remove the direct dependency on docker, when installing/executing winebuild.

[plata]

I like the idea to use a python library. docker-py could be an option.

[qparis]

Sounds good to me too

[qparis]

System calls have been replaced with docker-py. Should not be too hard to support remote Docker now