Task-number: QTCREATORBUG-3554

Task-Nr: QTCREATORBUG-2166

Patch by Fabo

It's now a part of mad-developer and should be on the device already.

Reviewed-by: Tobias Hunger

Reviewed-by: Kai Koehne

They need to remove them from their internal structure.

Make groups explicit instead of magic integer stuff.
That also makes group ordering explicit instead of magically working
(the way we happened to use it and the way unique id manager is
implemented).

Reviewed-by: Kai Koehne

Reviewed-by: Kai Koehne

Reviewed-by: Kai Koehne

Reviewed-by: Friedemann Kleint
Reviewed-by: hjk

Reviewed-by: Leandro Melo

Task-number: QTCREATORBUG-3189

Task-number: QTCREATORBUG-3371
Reviewed-by: Roberto Raggi

Reviewed-by: Erik Verbruggen

We need a feature which allows a more flexible binding
of MIME types and editors. This is definetely not the
way to handle it, but a temporary workaround.

Reviewed-by: con

So the scene rectangle is the bounding rectangle of all items.