Restructure; Add Parsers, Util Functions and Message Creators

[jkbmrz]

Adding the following utils functions:

• decode_detections: Decode the detections from neural network output tensors,
• unnormalize_image: Un-normalize an image tensor by scaling it to the [0, 255] range,
• create_detections_msg: Create a depthai message for an image array,
• create_image_msg: Create a depthai message for an image array,
• create_monocular_depth_msg: Creates a depth message in the form of an ImgFrame using the provided depth map and depth type,
  and adjusting the existing postprocessing nodes to these changes.

@kkeroo, some things to consider:

• could you please adjust + test your postprocessing nodes to the new utils functions
• I've added create_monocular_depth_msg despite you already have implemented something similar in create_depth_segmentation_msg. However, I think its better we keep the two tasks (segmentation and depth estimation) separated. EDIT: I see this was changed in the meantime and segmentation and depth are already separated. Will check how I can merge my code

@tersekmatija, could you please check the create_monocular_depth_msg function to confirm it's implemented as expected?

[tersekmatija]

Is this required? We seem to use it for cols and rows calculation, which we can simply get from the output shape of the tensor itself.

[jkbmrz]

Added in 92f2ea4. However, this automatic detection doesn't work non-square inputs as pointed out here.

[kkeroo]

• could you please adjust + test your postprocessing nodes to the new utils functions

I will test utils functions.

• I've added create_monocular_depth_msg despite you already have implemented something similar in create_depth_segmentation_msg. However, I think its better we keep the two tasks (segmentation and depth estimation) separated. EDIT: I see this was changed in the meantime and segmentation and depth are already separated. Will check how I can merge my code

Yea, probably we can delete create_depth_message() as you have your depth function, and we can leave create_segmentation_message as is.

[jkbmrz]

Yea, probably we can delete create_depth_message() as you have your depth function, and we can leave create_segmentation_message as is.

In 17ce753, I've merged the old depth message to monocular_depth message and deleted it. @kkeroo, can you check and confirm this is OK? EDIT: It's now called depth message.

[kkeroo]

The new depth message looks good. I tested new util functions and they work.

[tersekmatija]

Please address the one comment, then merge and we can update #5 to use this.