This patch completes the ACL added in [17ba87cbc](https://github.com/webmin/webmin/commit/17ba87cbc).
That change protected only the edit and save pages.
Users without environment-variable access could still change variables through delete, bulk actions, and moves.
This applies the permission everywhere and hides blocked controls.
It also applies create and delete permissions to variables and prevents job and variable endpoints from being mixed.
