Revision 894645

Refactoring for MimeEntity:
- now takes a simple InputStream in input and add the buffering internally.
- now wants a MutableBodyDescripor to be used for this entity (and not a parent reference like before) (MIME5J-156)
- MimeEntity/AbstractEntity do not more depend on Maximal/Default BodyDescriptor implementations.
- removed T_IN_BODYPART and T_IN_MESSAGE "dummy" states (they are no more needed) (MIME4J-152)
- Zero parts multipart messages were parsed as 1 empty part multipart messages. Fixed (MIME4J-152)
- Added testmessages for the zero part multipart issue (MIME4J-152)
- MimeEntity.skipHeader removed. Headless parsing is now done simply passing a MutableBodyDescriptor with the right contenttype and a custom startState to the MimeEntity class (no hacks inside MimeEntity) (related to MIME4J-153)
- MimeTokenStream headless parsing doesn't start from T_END_HEADER state anymore but from the following state (MIME4J-153)
- mimeStream renamed to mimePartStream (and also related methods).
- MimeTokenStream now proxy the stop() request to the root mime entity (implemented MimeEntity.stop()).