Add network per build

What does this MR do?

Add support for per-job Docker network creation, based on !609 (closed), and built on top of !895 (closed) (rebased on master). By nature of its implementation it also provides a workaround fix for corporate DNS resolution as outlined in https://github.com/docker/libnetwork/issues/2187, and may mitigate issues such as #1541 (closed).

Why was this MR needed?

There is a huge need of proper service discovery b/w the job container and the service container(s). Use cases include:

• Running a selenium grid peer to the build container which can see the build container (i.e. karma tests).
• Set up complex interdependent application stacks.

Are there points in the code the reviewer needs to double check?

I am relying on claims made by the original author that it 'works', but didn't actually run it myself.

Does this MR meet the acceptance criteria?

• Documentation created/updated
• Added tests for this feature/bug
• In case of conflicts with master - branch was rebased

What are the relevant issue numbers?

Based off of !609 (closed) and !895 (closed).

Closes #1042 (closed)

Partial fix for #1541 (closed).