Select Region of Interest

This script is designed to help the user select a region of interest to use with the set of images selected by the user. The boundaries can be set either by clicking and dragging, or with the text entry boxes. When this script is run, it will look for a config file called ROI_config.txt that specifies the region of interest. If no such file exists, it will be created when the user presses 'Save'. Saving will overwrite any previous information in ROI_config.txt. ROI_config.txt will be used by other scripts, such as image_diversity.py, Autotrace.py, and TrainNetwork.py.