Allow option to disable progress bar when using GenericDataLoader

[xhluca]

Right now, when using the data loader:

corpus, queries, qrels = GenericDataLoader(data_dir).load(split=split)

Tqdm will always show up. there should be a way to disable it, e.g.:

corpus, queries, qrels = GenericDataLoader(data_dir).load(split=split, show_progress_bar=False)

[root-goksenin]

Hey xhluca,

I also was not fan of tqdm. It was really annoying sometimes.
When I do not need it, I disabled it by using the environment variable.
os.environ["TQDM_DISABLE"] = "1"