Merge branch 'docs-updates' into 'master'

Docs updates

- Changed document to use 'Big Bang' vs. 'Umbrella'
- Updated default configmap / secrets names in configuration
- Replaced references to deprecated /examples directory
- Updated location of customer environment template (Customers/template)
- Cleaned up CONTRIBUTING and README
- Updated CHANGELOG

Will fix #2

See merge request platform-one/big-bang/umbrella!108