- added RFC1123 http date format helper
- added put_cookie_with_expiration_date as DATE_TIME
REQUEST: added `execution_variable' to provide a way to keep object attached to the request
and indexed by a string. A typical usage is a SESSION object
- HTTP_HEADER.string does not have the ending CRLFCRLF .. but just CRLF
- WGI_RESPONSE.write_header_text has the responsibility to handle the last blank line CRLF (separating the header from the message)
- HTTP_HEADER.string does not set anymore a default content type as text/html
- added WGI_RESPONSE.write_header_lines (ITERABLE [TUPLE [name,value: READABLE_STRING_8]] mainly as an helper method,
this way the WGI user does not have to know about the CRLF end of line
