Update metadata for image downloads

[LevanBokeria]

Currently, each species folder gets saved with a meta_data.json file which has an entry for each image, with each entry containing following information taken from the occurrence dataframe:

fields = [
    "decimalLatitude",
    "decimalLongitude",
    "order",
    "family",
    "genus",
    "species",
    "acceptedScientificName",
    "year",
    "month",
    "day",
    "datasetName",
    "taxonID",
    "acceptedTaxonKey",
    "lifeStage",
    "basisOfRecord",
]

[LevanBokeria]

Should add the following fields:

    fields = [
        "image_is_downloaded",
        "image_url_works",
        "image_is_corrupted",
        "image_is_thumbnail"
    ]

So when the download code is re-run, it will skip the downloading of a specific image if:

• its already in the folder
• if the URL is broken: this will save significant time, cause lots of them are broken
• if the image is corrupted or is a thumbnail, as marked by subsequent preprocessing steps (not yet developed)