1. Hyphenated labels are still accepted when parsing scoped keys (so 'sbt test-only' still works)
There is currently no timeline for removing this support for hyphenated keys.
2. Only camelCase is shown for tab completion.
3. AttributeKey.rawLabel provides the unnormalized label.
This should only be used to implement support for accepting hyphenated keys as input for compatibility.
4. AttributeKey.normLabel provides the normalized label (hyphenated converted to camelCase)
* split several source files
* move base settings sources (Scope, Structure, ...) into main/settings/
* breaks cycles. In particular, setting system moved from Project to Def