Optim-wip: Improve & fix LaplacianImage

[ProGamerGov]

• Improved the LaplacianImage code as part of removing the ToDo comment.
• Added "same" padding option to GaussianSmoothing.
• Improved the NaturalImage docs.
  • Also removed the built-in clamp squash function. It's inclusion was an aesthetic choice, and it's easy enough for users to add on their own.
• Added the new indexing argument for torch.meshgrid in GaussianSmoothing as it will be required in future PyTorch versions.
• Changed depreciated self.assertEquals to self.assertEqual.
• Use register_full_backward_hook instead of register_backward_hook for applicable tests, as the later is being depreciated.
• Added dtype tests to for image parameterizations & transforms.