[WIP] Updates to simplify PLT example and use new features
Some changes to PLT to support our workflow. Prelim support for TPUs. 

Still testing. 
I can't seem to find who is pushing the commits, but can whoever is doing that please add commit messages? This is really messy and impossible to go over as currently written.<|||||>Sorry, @BramVanroy . I didn't realize people were reviewing this branch. This is a WIP We are still trying to work this out with new pytorch-lightning / TPU changes. (Closing for now and will switch to a new review branch when it is working). <|||||>@srush No worries! Wasn't really reviewing, I was just curious which changes were being made - but then I saw those commit messages and I didn't know what to expect. 😄 