Move large data logic from DroneML to segmentmytif

[cwmeijer]

The DroneML plugin should have as little as possible data handling and pass the data (by means of a file path to the data for instance) to segmentmytif to do the actual handling and processing. Therefore as much as possible logic concerning data loading and handling currently in DroneML should be moved to this repo. See main.py for the entry point of the API.

See https://github.com/DroneML/segmentmytif/blob/main/tests/test_main.py for some integration tests, to help testing the logic.

@rogerkuou I think this was what we discussed today, if you meant something else, let me know.