Bounding box formats convertors

[Oleg42-prog]

Add functions to convert between different bounding box formats. I suggest adding the following formats:

• [ ] xyxy - upper left and lower right corners
• [ ] xywh - upper left corner, width, height
• [ ] cxywh - 'yolo like' format of the box, x, y - centre of the box, w and h - are half the width and height of the box respectively
• [ ] xyxyn - normalised (i.e. the bottom right corner of the image has coordinates (1, 1)) version of xyxy
• [ ] xywhn - normalised version of xywh
• [ ] cxywhn - normalised version of cxywh
• [ ] xyxyp - like xyxyn but in percentages (e.g. used in Label Studio)
• [ ] xywhp - like xywhn but in percentages
• [ ] cxywhp - like cxywhn but in percentages

[Oleg42-prog]

We have 3 different bounding box representations: xyxy, xywh, cxywh

And we have 3 different coordinates systems: base image, normalised, normalised in percentages

Totaly we have 3 * 3 = 9 bounding box formats.

Total number of all convertation functions is 81, and 9 of them is identyty.