- allow multiple arguments to a given method ???
  (other than passing it a list reference...)

- Config::Objective::DataType problems:
  - replace 'value_optional' and 'value_type' options with a reference
    to a subroutine to perform input validation?

- architecture:
  - make data types work recursively
  - allow usage of methods to access nested data.  Example:
      hash->find('key')->list_delete('foo');

