services_discovery: Partially fix service discovery. We yet need to find a way to properly get the localized name... grr.

Previously we properly initialized the localized name of the object in Open(). Now Open() also runs Run() so we are kind of stuck. Please fix.

As discussed on IRC. Yield was quite confusing.

By the way, the event management seems quite broken. Events may occur
before _Create returns (even before this commit)...

Avoid objects being detached asynchronously too early.
Side effect is that you cannot free your children in the destructor
(that would be a reference loop).

Fixes payload type overflow especially when using sout keep/gather.

It will allow correct YUVP rescaling and even anti-aliased support
if someone do it.

It will avoid useless picture copy.

(By the way, snapshot-id looks like a write only variable...)