Standardized scheme-eval command

[lassik]

For portability-testing a feature across many implementations, it would be great if we could do something like this:

docker run schemers/bigloo scheme-eval "(+ 1 (* 2 3))"

It would evaluate the expression.

• On success, write the results to standard output as Scheme forms, one value per line, and exit with code 0.
• On failure, write free-form info about the exception to stderr, and exit with nonzero code.

If this works consistently across containers (as scheme-script now does among many) it would be easy to write a runner script to launch containers for a test, collect and curate the results.

[lassik]

(Duplicate post of #15 due to a glitch in the GitHub UI.)