Setup should be simplified

[ewingjm]

Is your feature request related to a problem? Please describe.
The setup at the moment is a little bit more complicated than it needs to be. For example, it demands that repositories are structured (or perhaps restructured) in a certain way to conform to the Development Hub's expectations. Having to manually maintain the extract pipelines and scripts per repository is also time consuming.

Describe the solution you'd like
Solution extract directory could be configured on the solution records within the Development Hub. It may be possible for a single extract pipeline to be configured per project which then uses external build steps (e.g. from GitHub).