Improve Message Parser Robustness and Message Body I18N

Smack should not close the connection if the message body contains additional tags. Although specification says that the body must not contain any tags it is user input and it should not be possible for a user with an errornous client to send messages that close the connection of other users.

Additionally for the parser to correctly set message bodies in different languages that may occur in a message packet the patch fixes the faulty handling of localized bodies.
A message tag may contain an xml:lang attribute which sets the default language of the message. This attribute is now not ignored anymore when correlating the message bodies to a language. Every message body now has a language associated (no null language for the default language of the message or application at the moment the body was set).