Add well known handlers API

.htaccess

apps/settings/js/admin.js

apps/settings/lib/AppInfo/Application.php

core/Controller/WellKnownController.php

core/js/setupchecks.js

core/js/tests/specs/setupchecksSpec.js

core/routes.php

lib/composer/composer/autoload_classmap.php

lib/composer/composer/autoload_static.php

lib/private/AppFramework/Bootstrap/RegistrationContext.php

lib/private/Http/WellKnown/RequestManager.php

lib/public/AppFramework/Bootstrap/IRegistrationContext.php

lib/public/Http/WellKnown/GenericResponse.php

lib/public/Http/WellKnown/IHandler.php

lib/public/Http/WellKnown/IRequestContext.php

lib/public/Http/WellKnown/IResponse.php

lib/public/Http/WellKnown/JrdResponse.php

tests/Core/Controller/WellKnownControllerTest.php

tests/lib/Http/WellKnown/GenericResponseTest.php

tests/lib/Http/WellKnown/JrdResponseTest.php