Code changes:
 - Added two new enum values to ValidationResult - IS_POSSIBLE_LOCAL_ONLY and
   INVALID_LENGTH. Added more documentation to the existing values; see the
   javadoc for when these are going to be used. Note that the API for
   IsPossibleNumberWithReason has not yet been changed to return these values.
   IS_POSSIBLE_LOCAL_ONLY will be returned for some values which currently
   return IS_POSSIBLE, and INVALID_LENGTH will be returned for some values which
   currently return TOO_LONG.