Add IoU/GIoU for boxes

[twsl]

🚀 Feature

Motivation

IoU/GIoU are ametrics essential for the detection domain.

Pitch

Add metrics, for fast implementation these could be based on torchvisions functions.

Alternatives

Additional context

[Borda]

I think we can use this code, right? https://github.com/PyTorchLightning/lightning-bolts/blob/0.5.0/pl_bolts/metrics/object_detection.py

[twsl]

There is an even easier solution if we use torchvision. I can create a draft tomorrow

[Borda]

There is an even easier solution if we use torchvision. I can create a draft tomorrow

I would try to keep own implementations if possible :rabbit:

[jscottcronin]

@Borda - I can take this issue :)