Upgrade webpack and other frontend deps

Upgrades several frontend dependencies including webpack, several webpack loaders, karma, and a few of karma's dependencies.

This resolves a few bugs with webpack and karma including the broken reporting timer in karma, a few webpack-related deprecation warnings in karma, and some optimzation settings in webpack.

I've looked through each of the changelog entries for these dependencies and most of the changes are pretty minor/uninteresting, but it's good to stay on top of these things.