Write eval results to tensorboard

[xsacha]

The console is the only other place the evaluation is shown and this only stays around as long as your buffer isn't full. I think it's important for this to be in the tensorboard.

-------- RetinaFace Pytorch -------- Evaluating epoch 147 100%|████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 404/404 [01:43<00:00, 3.91it/s] Recall: 0.7351636132230178 Precision: 0.9029628486077838

I've noticed my recall and precision is lower than expected but wasn't able to follow it back because it was lost in the buffer.

[xsacha]

Thanks