98 deformable panoptic head

[Johansmm]

Full train-pipeline to train Detr and Deformable Detr with PanopticHead.

News:

• DetrPanopticCriterion and DeformablePanopticCriterion, based on PanopticCriterion

Updates:

• Detr and Deformable forward, to provide the correct backbone format: Input_projection for the last feature of backbone.output
  • In Deformable, backbone was changing to provide the same layers than detr.backbone. Also the encoder.output was provided in deformable_transformer.output.dict .
• Detr_panoptic forward update to get input_project directly from features[-1][0] and the correct mask format.
• Threshold boxes in inference given by default threshold values in detr.inference or deformable.inference

Fix other issues:

• Update ModelCheckpoint to save the top=3 checkpoints (as provided by the argument support)

Closes #98