feat(@angular/cli): add in-browser development error overlay

[clydin]

Implements the feature described in #3502 by leveraging the new capability in webpack-dev-server 2.3.0.

Closes #3502

[hansl]

Please rebase, I'm willing to consider it.

[clydin]

Done.

[filipesilva]

Looks like this, for reference:

[dancancro]

I'd like to be able to configure this off. Webpack is giving me warnings about missing classes that are not missing. The app runs fine. However, the overlay warning now means I can't use my app. Until now the warnings just appeared in the developer tools console.

I don't know what's causing these wrong Webpack warnings. I'd rather just live with them than spend a lot of time on it when an update is bound to eventually fix the problem.

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