This update uses a function to apply the z-index in each .scss file.
The function needs to iterate over a map of z-index values, so all of
the z-indexes end up in a single list and can be tracked more easily.
This allows us to manage all z-index values in a single location.
The loading bolt was being shown in several distinct places, which was
resulting in a glitch between completing onboarding and showing the
wallet ui.
Refactor such that the LoadingBolt component is only mounted once, in
the root component.
Rather than using relative paths for css imports - which can break when
we move files around - add our styles path to the webpack sass-loader
loader using the `includePaths` setting.
dfat
Tom Kirkpatrick
Jack Mallers
Ben Woosley