IDEA: Automatically install missing packages(?)

When launching futures on remote machines ( e.g. cloud VMs), not all packages needed for the future to be evaluated may be installed. If a required package is missing, then a run-time error will occur and `value()` will throw an exception.

It might be useful to have an option to make futures automatically install packages that are missing, e.g. `future.package.on_missing = "install"`.

A possible complication is that when multiple futures try to install the same package on the same machine / account / file system at the same time the installation might fail.