Geometry_Engine: IsPlanar for PolySurface and CompositeGeometry are wrong

#### Description:

The IsPlanar check for the named methods only check if their subparts are planar, but do not check if they are all co=planar with each other.

#### Steps to reproduce:

Create a composite geometry/planar surface with multiple planar elements, that are not co-planar with each other.

#### Expected behaviour:

For method to check if all of the inner objects are co-planar, rather than if the individual elements are planar.

#### Test file(s):