Copy-paste-laziness

Update the workspace when changing the target

Update webpack config and vm usage to match updates in scratch-vm

Also make the toolbox actually get used by scratch-blocks, and update the import of scratch-blocks to use the new shimming method.

This way we can have a consistent style for Node and web code.

Add skeleton toolbox component

Thanks to babel-loader and babel-eslint, we can use the same linting everywhere.  This makes our imports easier since we don't need to think about the extension.

Also export things more succinctly in src/index.js