Streamline env variables

[danisyellis]

Let's do this after converting the repo to TypeScript

Right now, the defaults for our env variables aren't very standardized. Some are optional, some aren't, some can be blank, others can't, etc. We have numeric entries that must be present, but should be allowed to be zero and we have a string (TIMEZONE) that is totally optional, where "" is treated as if it's missing.
We may want to change some of them to use non-string true and false. It looks like this package would allow us to do that in an .env file https://www.npmjs.com/package/dotenv-parse-variables