Allow spaces in bbox

[skorper]

We should improve the flexibility of this software by allowing spaces in the bbox param, like so:

podaac-data-downloader -c MUR-JPL-L4-GLOB-v4.1 -d ./data --start-date 2022-01-01T09:00:00Z --end-date 2022-01-10T09:00:00Z -b="-75.61, 38.4, 84.1, 50"

The current behavior is rigid and will fail if the above request is provided. Such a request does work with the 1.15.0 UAT subsetting feature which allows spaces.