Make netdev find_anchors work on an already saved dataset

The netdev find_anchors functionality is crucial to producing a trainable network - in essence it sort of tells the network a little more about what to expect from the dataset. However in its current form it only accepts raw datasets, the image and label files themselves, and not the already processed .pt datasets that are saved by the DataParser class.

The task here will be to add the functionality for find_anchors to accept a .pt dataset, unpack it, use the label data to find the anchors, and output it like normal.