consolidate accept classes into the single AcceptCharset class

Author: mmerickel

docs/api/webob.txt

@@ -30,26 +30,13 @@ methods:
 
 .. autoclass:: Accept
    :members: parse, header_value, parsed, header_state, __init__, __add__,
-         __bool__, __radd__, __repr__, __str__,
+         __bool__, __radd__, __repr__, __str__, copy,
          accept_html, accepts_html, acceptable_offers, best_match
 
 .. autoclass:: AcceptCharset
-   :members: parse
-
-.. autoclass:: AcceptCharsetValidHeader
-   :members: parse, header_value, parsed, __init__, __add__, __bool__,
-         __contains__, __iter__, __radd__, __repr__, __str__,
-             acceptable_offers, best_match, quality
-
-.. autoclass:: AcceptCharsetNoHeader
-   :members: parse, header_value, parsed, __init__, __add__, __bool__,
-         __contains__, __iter__, __radd__, __repr__, __str__,
-             acceptable_offers, best_match, quality
-
-.. autoclass:: AcceptCharsetInvalidHeader
-   :members: parse, header_value, parsed, __init__, __add__, __bool__,
-         __contains__, __iter__, __radd__, __repr__, __str__,
-             acceptable_offers, best_match, quality
+   :members: parse, header_value, parsed, header_state, __init__, __add__,
+         __bool__, __radd__, __repr__, __str__, copy,
+         acceptable_offers, best_match
 
 .. autoclass:: AcceptEncoding
    :members: parse