[feature] --silent

[jbottigliero]

• Adds --silent option for suppressing output to stdout [Feature: Support --quiet on the command-line #22]

What kind of change does this PR introduce?
feature

Did you add tests for your changes?
Yes - the test is a duplicate of test/binCases/stats/multi-config, with some modifications to try and force more output.

If relevant, did you update the documentation?
webpack/webpack.js.org#1781

Summary
Related Issue: #22

This is possibly a naïve implementation, but seems to get the job done now that webpack-cli is it's own module.

Currently this change will not suppress output for the "non-compilation" commands. I can update this PR if it should, however most seem like they would not benefit from a --silent flag.

As far as the name for the actual flag, I can change that as well... @ev1stensberg previously mentioned -s/--save was taken at one point, but it looks open now?

Does this PR introduce a breaking change?
No

[webpack-bot]

Thank you for your pull request! The most important CI builds succeeded, we’ll review the pull request soon.

[evenstensberg]

Thanks! Could you remove the quiet flag and its code while at it? Cc @bebraw

[jbottigliero]

@ev1stensberg – I'm not so sure it was ever actually implemented. I'm not seeing anything in webpack@[next|master|webpack-1|webpack-2], or here... and based on the conversation in webpack/webpack#490 it seems like it could have just been abandoned before adding a ticket here (#22).

[evenstensberg]

Remember adding the feature, maybe it has been discarded. I'll check and get back to you during the day