Replace copy configuration with automatic copying via Webpack

As mentioned in #33, the current way how copying assets (fonts, images) work is by manually configuring paths for a copy task. This works a bit against the concept of Webpack, which should automatically resolve dependencies and then copy them.

I can provide these changes via a pull request, as I already updated this behavior in my projects which are using patternlab-edition-node-webpack. So it's tested in multiple production projects.

Start by tracing the current manually configured copy task for fonts and images and read the related discussion in issue #33. Compare the existing asset flow with Webpack dependency resolution, then verify that required supporting assets are copied without manual paths.

Written by the indexing model from the issue text.