Automatically set environment variable with current morph api key

[mlandauer]

This is to make it easier for one scraper to access the data from another scraper with the api. You don't actually have to embed the secret key yourself. It's just "magically" available.

Some other environment variables that we could set if they're useful:

• The current scraper name
• The current scraper user

[tmtmtmtm]

:+1: I'm increasingly writing scrapers that interact with each other, and sometimes forget to set this until after the first run errors.