Implement high level trait computation methods

[talmo]

With #51 (and after #52 is addressed), it will be extremely convenient to have a high level method that can just take a list of paths, automatically infer the appropriate pipeline to use and run it in batch using the compute_batch_traits method.

This function can go in the pipeline_traits module and be called compute_traits (outside of the class) for convenience so you can do something like:

from sleap_roots import compute_traits

plant_filenames = ["a.h5", "b.h5", "c.h5"]

all_traits = compute_traits(plant_filenames, write_individual_csvs=True, write_csv=True, csv_filename="all_traits.csv")