Fix QQuickVisualDataModel test failure.

Fix QQuickVisualDataModel test failure.

When connecting the source object's notify signals to the proxy object's
the objectName property wasn't being skipped, this didn't matter much
before because the object name property didn't have a notify signal
and so was skipped anyway.  Adding a notify signal resulted in all the
signal connections being off by one.

The object list proxy meta-object also shouldn't assume that QObject
has only and only ever will have one property.

Change-Id: I238e05153446cbfdceea643963e3a26f665e41a1
Reviewed-by: Martin Jones <martin.jones@nokia.com>