If property metadata fetches GroupSequence, skip

[KDederichs]

Q	A
Branch?	2.7
Tickets	#4613
License	MIT

Allow the Schema Factory to generate schemas if one of the Classes is a GroupSequence Provider.
It seems the Factory is picking up on the Getter defined by the interface and is trying to add it as property.

Now the question is if we should fix it like this OR add a section to the docs that explains that people have to tell the serializer to ignore the getter as that also seems to fix it.

Let me know what you want to do with this :)