fix(registerState) canonicalize state names

- State names are expanded to full dot-notation
- Absolute srefs work with `parent`-defined states

BREAKING CHANGE: code comparing against state names will need to use the fully-expanded dot-notation form. This change is most likely to affect users who use the `parent` key in state definitions to manage the state hierarchy. This includes calls to `$state.is()` and `$state.includes()`.