Latest Compendium materials JSON causes errors

[markbandstra]

The latest version of the materials data from the PNNL Compendium cannot be parsed by the current version of becquerel.

Downloading the latest JSON and placing it into becquerel/tools and calling bq.tools.force_load_and_write_materials_csv() causes the following error:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File ".../becquerel/tools/materials.py", line 196, in force_load_and_write_materials_csv
    materials = _load_and_compile_materials()
  File ".../becquerel/tools/materials.py", line 26, in _load_and_compile_materials
    data_comp = fetch_compendium_data()
  File ".../becquerel/tools/materials_compendium.py", line 63, in fetch_compendium_data
    names = [datum["Name"] for datum in data]
  File ".../becquerel/tools/materials_compendium.py", line 63, in <listcomp>
    names = [datum["Name"] for datum in data]
TypeError: string indices must be integers

It seems from looking at a JSON from a few months ago and a JSON downloaded today that the difference is that the older JSON has a structure that parses into a list of dicts:

[
    {
        "Comment": "Material 1 data",
    },
    {
        "Comment": "Material 2 data",
    }
]

whereas the new format parses as a dict and the list of material data are inside of it:

{
    "siteVersion": "0.1.1",
    "data": [
        {
            "Comment": "Material 1 data",
        },
        {
            "Comment": "Material 2 data",
        }
    ]
}

So the solution is easy: to check for the data that get loaded and use data["data"] if it is the new format.

Both versions appear to contain 411 materials, but I have not checked whether any of the data for individual materials differ.