add some flatMap tests
Add examples + bug fixes

- add Calculator and Calculator2 examples
- put c.untypecheck in filter, map and "value" expansion, to prevent the "scalac: Error: Could not find proxy for x: Int in List(.." error
- fix repsep type from repsep[T](p:Parser[T],sep:Parser[T]):Parser[List[T]] to repsep[T,U](p:Parser[T],sep:Parser[U]):Parser[List[T]]