remove previously deprecated code

[davidism]

These uses showed a deprecation warning in 2.3, and are now removed for 3.0.

• Bytes are no longer supported where strings are expected. The charset and errors parameters to various functions are removed, as are the attributes on Request and Response.
• Remove our copy of urllib.parse from our urls module, in favor of using the built-in module directly.
• Authorization and WWWAuthenticate are no longer dicts, although they retain some mapping behavior. Digest properties are no longer handled specially. http.parse_authorization_header and parse_www_authenticate_header are removed.
• Various unused parameters to http header parsing functions are removed.
• FormDataParser parse_functions and get_parse_func are removed. Invalid content type application/x-url-encoded is not supported.
• generate_password_hash and check_password_hash no longer support basic hash+hmac methods. Only Scrypt and PBKDF2 are supported.
• Test client no longer uses CookieJar.
• wsgi.make_chunk_iter and make_line_iter are removed.