changed to ccabs and rework folder structure and codestyle

- changed composer.json
- changed folder structure
- changed to ccabs 
- changed the code style to cca-code-style

Please review https://github.com/cboelter/metamodels-attribute_timestamp/blob/40e34d28aa7d1fe60d28f3c86c4d32d57a65db98/src/MetaModels/Attribute/Timestamp/Timestamp.php#L164-L201 is this the right way for global handling?