Re-introducing Interval types

- Converter knows about them
- Emitter knows how to emit them
- Type maps added to package object
- Add IntervalSpec
- Re-work RangeSpec
- Add Interval type to Bits
- Data knows hot to clone them
- MonoConnect can connect them
- core package knows about literal creation
- IR knows about them
- IR gets RangeType
- RangeTransform modernized