Add URL support to cp-worker

[ErinWeisbart]

Support using URLs for file paths.

Currently, CellProfiler (when installed from source) can load from s3:// paths

[bethac07]

import re 

    if url.startswith("s3"):

        bucket_name, filename = (
            re.compile("s3://([\w\d\-.]+)/(.*)").search(url).groups()
        )