flesh out the customer-facing guide

...rprise-customer-facing-guide/customizing-drill-through.md

docs/enterprise-customer-facing-guide/embedding.md

docs/enterprise-customer-facing-guide/overview.md

docs/enterprise-customer-facing-guide/sandboxes.md

docs/enterprise-customer-facing-guide/setting-up-sso.md

docs/enterprise-customer-facing-guide/start.md

docs/enterprise-customer-facing-guide/white-labeling.md