Refactor vtkDebugLeaks construction.

vtkDebugLeaks registers instance by class name, which worked well for
many years. However, now that we have more templated code, this is
becoming difficult. For instance, "template <typename T> vtkBuffer<T>"
would be identified as "vtkBuffer<T>" when registering with
vtkDebugLeaks, but deregistered with the compiler dependent
typeid(vtkBuffer<T>).name() string returned from GetClassName().

This patch moves vtkDebugLeaks registrations to the method
vtkObjectBase::InitializeObjectBase(), which must be called after the
vtkObjectBase is instantiated. This ensures that objects are
registered using the same string as when they are destroyed. In
general, a call to "new vtkSomeClass" must be followed by a call to
InitializeObjectBase on the new instance. The common ::New()
implementation macros in vtkObjectFactory will ensure that
registration happens correctly.

Two notable exceptions are vtkCommand and vtkInformationKey
subclasses. These do not require any specific handling for
vtkDebugLeaks registration.

See discussion at:

http://vtk.1045678.n5.nabble.com/Proposal-Simplify-vtkDebugLeaks-registration-td5740222.html