Add Annotation for System Environment Variables

[Hancho2009]

resolves #167

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[nipafx]

Oh, accidentally closed this by pushing my master to your master (it would be more convenient to do this in a branch). Fixing it now...

[nipafx]

Sorry, I couldn't push to your master, so I pushed your commits to Pioneer's repo - see system-environment-variables. If you fetch that branch and push it to your repo, you can open a new PR - in case you're unsure how to do that:

# if you didn't add the Pioneer repo to your local clone of your fork
git remote add upstream https://github.com/junit-pioneer/junit-pioneer.git
git fetch upstream
git checkout system-environment-variables
git push system-environment-variables
# now Git may complain that the remote branch doesn't exist,
# but it should explain how to do it with additional flags

Sorry again. 😳