Expose endpoint for API

[mcab]

Addresses #8.

Since we'll be using this with mcab/flightplan, we need a way to communicate the data.

This is the scaffolding for such.

[mcab]

We're actually pretty close.

/api/v1/schema isn't returning the proper routes, though. This can be bypassed with a static generation, but probably understanding why it's not generating in the first place is more important.

Additionally, this is ReadOnly for now.

[mcab]

I've been working on this for a bit.

• ~Can't properly get the human-readable equivalents for choices nested in ArrayFields~.
• Can't get an absolute path to media using ImageRenditionField.
• Can't get the base image to display over DRF.

The bottom two would probably be fixed if we used Wagtail's API, but I'm iffy on the declaration on how to get data from it. Since Bat is a Django model, we should stick to using that instead of going through Wagtail's API.

Also, the ArrayField and mapping seems a bit weird. Internally, DRF sees it as a ListField, but there's no way to link the items in the List to their human-readable equivalent. It still probably uses get_FOO_display(), it's a matter of calling it properly.

[mcab]

We ended up being able to serialize values back to their human-readable counterparts. Definitely not DRY, but since there is no way to pass which field needs the proper counterpart, I guess this is okay™.

[mcab]

In order to at least have a basis for the API endpoint / structure, I'm changing this to at least have one model exposed over API.

This is so we can address #11, knowing we have an endpoint for our API.