MDL-55127 mod_data: Search entries fixes

MDL-55127 mod_data: Search entries fixes

- If the database contains has than 4 valid fields all fields from the 4th one
  to the last one will be merged into the 4th one so we index all entry contents
- get_content_value now receives the whole data_content record as fields may need
  other values than just the content to prepare the value
- phpunit database generator changes to separate checkboxes from radio buttons options
  and to separate multimenu options from menu options