Several Improvements for Calibration Tool

[onurtore]

Hi!,
I have been using calibration tool for a while, and I believe there are some features that definitely improve the output of the calibration. I want to create PR for them, but first wanted to get your opinions so that I do not spend unnecessary time.

1. Calibration Requirements

Currently, one of the calibration requirement is to have 40 picture of the pattern. I believe, this should be parametric.

Opencv fish-eye calibration implementation uses this paper, and the normal calibration tool uses this, both of the papers does not require 40 images for the calibration, and this number depends on many of the features of the calibration pattern, or the lens type. The default can be 40, but otherwise I believe hardcoding this as 40 is wrong.

2. Save and Load option for calibration data

When I used this tool, I realized that many of the calibration images are blurred, I now there is an option for --max-chessboard-speed however, i believe loading and saving the calibration data through gui will give much more flexibility. The idea is, to ability to save images, and their corresponding parameters to a folder, and then reloading them with the help of gui, this way users can modify/delete/add new images and parameters to the calibration.

I realized that there is a tar calibrator, and it is kinda doing what I referrred, but I believe adding this feature to camera calibrator is a good option.

3. Verbose option

I believe, it will be beneficial to add verbose option to see the re-projection error, number of images and number of control points during the calibration.

[JWhitleyWork]

@onurtore I'm fine with all of these. Please make sure to implement them in separate PRs. Thanks!