[TASK][!BREAKING!] Adds a new author related plugin and the new author table.

Classes/Controller/NewsByAuthorController.php

Classes/Controller/SingleViewController.php

Classes/Domain/Model/Author.php

Classes/Domain/Model/News.php

Classes/Domain/Repository/AuthorRepository.php

Classes/Domain/Repository/NewsRepository.php

Classes/UserFunction/AddAdditionalMailRecipients.php

Classes/Utility/BackendNewsUtility.php

Configuration/FlexForms/NewsByAuthor.xml

Configuration/TCA/Overrides/pages.php

Configuration/TCA/Overrides/tt_content.php

Configuration/TCA/tx_sgnews_domain_model_author.php

Configuration/TsConfig/Page/NewContentElementWizard.tsconfig

Configuration/TypoScript/Common/setup.typoscript

Resources/Private/Language/de.locallang_backend.xlf

Resources/Private/Language/de.locallang_db.xlf

Resources/Private/Language/locallang_backend.xlf

Resources/Private/Language/locallang_db.xlf

Resources/Private/Partials/SingleViewSchema.html

Resources/Private/Partials/Teaser.html