Image Viz module revamp

[vierja]

It was build as a debugging tool but it adds real value when being able to view intermediate images in TensorBoard.

We should:

• [ ] Revamp the code
• [ ] Remove functions without a clear objective
• [ ] Avoid duplicated code when post processing raw Tensor values
• [ ] Use consistent colors for GT, Anchors, Predictions
• [ ] Add text tags to Objects Detection visualizations