Make the consulting part of the project-flow optional

[marcoow]

The part on consulting in the project flow (https://github.com/simplabs/playbook/tree/master/project-flow/consulting) is very specific to our offering and we don't want to publish that as part of the generally applicable playbook. We'll want to structure the content so that that part can be removed and everything else will still make sense.

[marcoow]

closing this as all of the content for this is already separate from the rest of the project procedure