Add importing of ingredients from standardized sources

[AustinGrey]

Adding ingredients manually can work for basic macro nutrient tracking and inclusion into recipes, but standardized sources of nutritional information exist. These sources can provide finer detail and nutrition data not included on consumer labels (e.g. density, useful for conversion between volume and weight measures). Oftentimes this data is collected with government funding and is therefore freely available, others are crowd sourced projects.

Pants could offer importing from these sources. Either a bulk import of everything (simple) or a search and import of individual foods (more complex, but better user experience). We wouldn't have to ship this data with PANTS, but could provide an offer to automatically download the files, or links to where the files could be downloaded

• https://fdc.nal.usda.gov/download-datasets.html
  • US funded and provided research
• https://world.openfoodfacts.org
  • Crowd sourced data, offers barcodes lookup, which opens the possibility of simply scanning a barcode to import.

I know this is a 'feature request' more than a bug or issue, but I dont think there are any issue labels setup in this repo. I'll label it if those become available.