Added learning schemes with restarts, to have similar options to the PPON paper. Currently StepLR_Restart is not yet working, but MultiStepLR_Restart does work and manual steps to change the LR can be added to have the same behavior as in the PPON paper.
Added a control mechanism for MS-SSIM for when the patch size is not large enough to allow images at the smallest scales to be larger than the defined kernel size window for the Gaussian function.
Some general fixes to the code and to make the training more similar to the PPON paper.