add property aspectRatio

[lpatiny]

aspectRatio can be calculated at the level of mbr, feret and also just by taking into account the width and height of the ROI.

Not sure however that everybody agrees if it is width / height or height / width

• "Aspect ratio is defined as ratio of the object height to its own width." from https://aip.scitation.org/doi/pdf/10.1063/1.4958602