Interval stuff

- fix interval lit emission, upper and lower bound are the same as value
- Some cosmetic line length changes in Bits.scala in Interval code
- More tests for IntevalSpec
- Some basic cleanup of IntervalSpec
- Create some utilities for testing Intervals in Util
- Cleanup in Bits
  - break up long lines in Interval
  - clean up some stale comments
  - added more scaladoc on interval methods
  - added some more object utility methods for interacting with BigDecimal