Add support for facility_type_processing_type meta extended field

[jwalgran]

Overview

In an attempt to avoid confusion the data submission process we will be putting a single facility_type_processing_type column in our upload templates rather than separate facility_type and processing_type columns. Though we are unifying the fields in the template we still want to create separate extended fields for each field type. Supporting this is a simple change because our processing was designed to handle either value type in either field.

We also add str to the ExtendedField model in an attempt to make the list view in the Django admin more helpful.

Connects #1655

Demo

Testing Instructions

• Log in as c2@example.com
• Upload ETEST2combofield.xlsx and run ./tools/batch_process {list id}
• Refresh the list page to see the updated row and click the link to view the facility. Verify that all the extended fields are filled in.
• Brows http://localhost:8081/api/docs/#!/facilities/facilities_create and authenticate with Token 1d18b962d6f976b0b7e8fcf9fcc39b56cf278051
• Submit this record browse the resulting record, and verify that all extended fields are created.

{
    "country": "US",
    "name": "API Meta Field Testing",
    "address": "200 Main St Philadelphia PA",
    "number_of_workers": 123,
    "parent_company": "Yet another parenct co",
    "facility_type_processing_type": "cut|warehousing",
	"product_type": ["pants", "suits"]
}

Checklist

• fixup! commits have been squashed
• CI passes after rebase
• CHANGELOG.md updated with summary of features or fixes, following Keep a Changelog guidelines

[jwalgran]

Sorry for the extra notification, @TaiWilkin. I moved the assignment over to Emily to balance the review load.

[emilyhu0106]

Looks all good! A very nice and sleek implementation

[jwalgran]

Thanks for the review.