Add a FIXME

The class in this test if effectively a template typedef.
Add a virtual copy method to Shape
Ensure shape works on Form pointers.

The methods look odd, as pure virtual methods which override a pure virtual
method in the base, but it is necessary so that if the method is called on
this interface, the return type is correct.
Fix memory leak in AreaProperty

The property was not deleting the shape object it owned, but adding the
delete was not enough. When the property is copied, it is necessary to copy
the shape object. In order to verify, add an integration test which
simulates the normal scenario of copying properites, just like in the
StatisticsPropertyintegration test.