Created a family of files mapping C++ STL's istreeam & ostream classes.

istream.hpp

    Defines boost::python::converters::istream<T>

ostream.hpp

    Defines boost::python::converters::ostream<T>

return_istream.hpp

    Defines the boost::python::return_istream_object return_value_policy
    and the boost::python::make_istream_type_object template for registering
    converters with Boost Python

return_ostream.hpp

    Defines the boost::python::return_ostream_object return_value_policy
    and the boost::python::make_ostream_type_object template for registering
    converters with Boost Python

ios_base.hpp
    Base template for istream and ostream templates

return_iostream_base.hpp

    Common templates for return_istream and return_ostream headers