Added custom object detection folder with all required files

[shanky1947]

I have added a folder named custom_data which has required folders and files for custom object detection in a specific required format. It has a python and jupyter notebook file that has all commands to run yolov3 on the darknet for custom object detection. The main commands are in Linux. Scripts to make required text files for image and label locations that are required by darknet are in python. It also contains a detector.data file which has required parameters and a custom.names file which has class names. Config file for custom object detection for 2 classes is added in cnf subfolder. It can be modified for specific number of classes.

Issue No.- #8046