Changed onboarding assumption to local first

The assumption has changed to support the simpler and most likely way more common case of single repo
sidecars instead of assuming that people want to put their sidecars of all their repos into a central folder.
Now each repo can own their own sidecar folder which makes versioning a lot easier out of the gate. You can still
create cross-repo relationsships but it is an opt-in function now. Otherwise it is assumed that you stay within the repo.

The advanced option is still there to organise all repos sidecars in a central folder or mix and match strategies. So some repos
can use the shared system and some can stay local.