Extracting HTTP_HEADER_BUILDER from HTTP_HEADER
  to provide useful interface on WSF_RESPONSE,
  and make WSF_SESSION easier to use.
Added comments, used better parameter names.
Added alias "[]" to `item', to get header value for a header name.
Added assigner for `item' to make it easier to add header item without confusing key and value.
Better parameter names (more explicit)
renamed HTTP_HEADER_BUILDER as HTTP_HEADER_MODIFIER
Added comment to explain why conversion to string 8 is safe
Replaced notion of session uuid by session id which is more generic (could be a uuid, or something else).
Use STRING_TABLE for the implementation of session data container.
Added a few missing comments.
check that cookies data is valid string 8 to follow assertions.
debug_output can return a string 32, so avoid truncated unicode value by returning a string 32 value for `debug_output' .
Support for unicode error message for the ERROR_HANDLER.as_string_representation: STRING_32
and as well for debug_output, this avoid unecessary unicode string truncation.
Apply recent change on error_handler interface to support unicode error message in response.
Minor change to avoid unecessary conversion from eventual immutable string 8 to string 8.
Merge pull request #128 from jocelyn/response_header

Extracting HTTP_HEADER_BUILDER from HTTP_HEADER
Improving wsf session usage
Various unicode related improvement for router and error library.