[TASK] #189 #158 #180 #190 Add services with custom templates for external content

Classes/Service/JsonImportService.php

Classes/Service/StaticFileGenerationService.php

Configuration/TCA/tx_sgcookieoptin_domain_model_optin.php

Configuration/TCA/tx_sgcookieoptin_domain_model_service.php

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

...es/Public/Icons/tx_sgcookieoptin_domain_model_service.svg

Resources/Public/JavaScript/cookieOptin.js

ext_tables.php

ext_tables.sql