Add codes in labelling to ensure tiles inside bbx

[SereinJannie]

Background

A bug was recorded in #176. In my testing, the tiles written in the label files after running the code label-maker labels are partly out of the bounding box provided inside the config file. I have added a checking function for this situation.

Changes

Inside the file label.py add the following function right before the function make_labels

Inside the function make_labels, update the variable tile_results before writing out labels

This would ensure the file labels.npz and classification.geojson not contain any tiles outside the bbx