[TASK] introducing domain model for the plugin (CE) configuration
[BUGFIX] fixing content object access
[BUGFIX] fixing typo in datamapper map call for pi configuration
[TASK] adding TCA configuration for pi conf + array_map on flexform vals
[TASK] refactoring into flexform domain object

This allows a more centric approach for retrieving the class
attribute configuration string.
[TASK] refactored the class attribute configuration
[TASK] adding domain logic regarding language output inc. fallback
[BUGFIX] adding identity to plugin configuration
[BUGFIX] removing singleton state of asset services