Can't delete box if created bottom right point first

[MattKleinsmith]

Warning: Click the top right point first, if using the current version of the repo.

Solution 1: Swap point_1 with point_2 if point_1 is the bottom right point. This solution will help with the VOC danger mentioned here: https://github.com/Cartucho/yolo-boundingbox-labeler-GUI/pull/6

Solution 2: Modify get_close_icon and draw_close_icon, and any other related functions

[Cartucho]

@MattKleinsmith I noticed this yesterday! My idea to solve is:

• The bounding box only shows the "delete" button if currently selected
• To select the bounding box we must do a double click

Selecting the bbox would also be great since we could later add an option to quickly resize and re-label the bounding box.

[Cartucho]

@MattKleinsmith It's done, now we can only delete if we select that bbox, it also deals with multiple bboxes goes for the smaller one:

I'm not sure if I thought of all the possible cases, but it is surely more robust now.