Add PrivateNet container to CLI

[revett]

Closes #69 🍓

Problem

The neo-local start command does not start the neo-privatenet container.

Solution

Add it as a new service so that it is included within the start command.

Checklist

• [x] I have ran the tests locally.
• [x] I branched off of the develop branch and not master.
• [x] I did not change the VERSION file.

[revett]

@nunojusto Ready for re-review 👍