"-sort" flag on "checkenv show"

[zomglings]

Currently, checkenv show prints environment variables in the order that it receives them.

This makes it difficult to debug env files with many variables across different machines because the order in which variables are defined is frequently different on each machine. It also makes it hard to diff against old versions of files.

So either the default behavior of checkenv show should be:

1. to sort the env vars alphabetically by name (with potentially a -nosort flag in case user wants to skip sort) OR
2. to not sort the env vars but give users a -sort flag that forces the sort