Environment Interdependencies

[Shadow53]

Allow an environment to require other environments to be true.

The simplest example is unix = ["linux", "freebsd", "macos", ...] where each one is an environment matching the appropriate os.

A more useful example is personal_machine = ["my_laptop", "my_desktop", ...] so that personal files don't accidentally get scattered around a work machine that I use programming dotfiles on.

Will definitely add some complexity to how environments are processed.