This commit moves the code adding @id to AsyncClient and SimpleClient,
instead of on the lower level send_stanza helper, which seemed to only
be used internally.
Support is also added for Component.
This removes the addition of @id on elements like <auth/> or <bind/>,
which probably weren't required anyway?
Signed-off-by: Maxime “pep” Buquet <pep@bouah.net>