v3.3.1

Fix support for import! in _variables.yaml

- The ReplacePlugin resulted in issues where requires and process.env replacements
were done in the same yaml file. Switching to a loader (which runs earlier in the chain)
resolves this conflict issue..
- Added example of shared footer for in the app.hbs, using a dynamic year, and the language in scss.
- Improved in-code documentation to make the usages a bit more clear.