Factor out EXTRACTED_IMAGE_DIR

[lamby]

We use EXTRACTED_IMAGE_DIR in a few places in the code, eg in prediction/src/algorithms/identify/prediction.py:

21:EXTRACTED_IMAGE_DIR = "data/extracted/"

This should be factored out into a more suitable location (eg. a setting or configuration - see elsewhere for prior art).

It should also use os.path.join for extra bonus points!

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[DrAmygdala]

Hi,

Could I work on this one? This is my first issue here.

Thanks