GraphService.findAllByProperty(prop, val) doesn't filter by the service's model type.

GraphService.findAllByProperty(prop, val) doesn't filter by the service's model type.
That's because FramedGraph#getVertices(key, value, type), which it uses, doesn't filter by type, it only frames the vertices as such type.

This change adds
GraphService.findAllByProperty(prop, val, boolean filterByType)
which allows optionally filter by the service's type.

The reason not to make it the default (or the only) behavior is that it has performance drawbacks - all items have to be checked using type.isInstance(model).