Support of score attribute in KITTI detetion

[yasakova-anastasia]

Summary

How to test

Checklist

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# Copyright (C) 2021 Intel Corporation
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# SPDX-License-Identifier: MIT

[yasakova-anastasia]

@zhiltsov-max, Datumaro does not save a value in the detection annotation.
From the README about this value:
score : only for results: Float, indicating confidence in detection, needed for p/r curves, higher is better.

Should we keep it when this value is present? If so, how? As an attribute?

[zhiltsov-max]

If this is a regular attribute in this format, then yes. Other formats (COCO, ...) use the score attribute name.