Feature: Improve watch functionality

[bebraw]

Do you want to request a feature or report a bug?

Feature.

What is the current behavior?

webpack --watch works, but it's not ideal in all cases. Perhaps something else than Chokidar would work better esp. with newly added files. See webpack/webpack#1863 for reference.

What is the expected behavior?

webpack --watch should be more robust (works with more cases).

If this is a feature request, what is motivation or use case for changing the behavior?

Improved user experience.

[SpaceK33z]

See webpack/watchpack#41 for a proof of concept for moving from chokidar to sane.

[SpaceK33z]

Dupe of webpack/watchpack#36 / webpack/watchpack#26.