Add DeOldify Model

[wconstab]

Follow instructions at https://github.com/pytorch/benchmark/blob/master/torchbenchmark/models/ADDING_MODELS.md

Model source: https://github.com/bwasti/DeOldify

This model has already been forked and modified as part of an earlier hackathon, so while it needs work to get into the current benchmark format, the install/data/train steps should already be clear. Script/tracing has already been attempted without success, so that can be skipped.