Merge branch 'new_version_4_1' into 'master'

Classes/Command/SendMailCommandController.php

Classes/Controller/MailController.php

Classes/Controller/QueueController.php

Classes/Domain/Model/Mail.php

Classes/Domain/Model/Template.php

Classes/Domain/Repository/MailRepository.php

Classes/Domain/Repository/TemplateRepository.php

Classes/Example/Register.php

Classes/Service/BackendService.php

Classes/Service/MailTemplateService.php

Classes/Session/PhpSession.php

Classes/Updates/UpdateGermanAsDefault.php

Classes/Updates/UpdateLanguages.php

Classes/Updates/UpdatePidToSiteRoot.php

Classes/Updates/UpdateSendingTimes.php

Configuration/TCA/tx_sgmail_domain_model_mail.php

Configuration/TCA/tx_sgmail_domain_model_template.php

README.md

Resources/Private/Language/de.locallang.xlf

Resources/Private/Language/de.locallang_db.xlf