offload utils into another file

[Mayukhdeb]

This will make app.py much more readable. We can remove all of the stuff spanning from

devolearn-web/app.py

Line 17 in 1294a4f

def onnx_segment_membrane(input_image, threshold):

to

devolearn-web/app.py

Line 86 in 1294a4f

def scale_model_outputs(scaler_path, data):

into a completely different file called utils.py to make it cleaner.

Ideally, app.py should only contain streamlit related stuff, and not core backend operations.