Translate files with InstantTranslate: Enable it to turn the feature of via configuration

The complete feature of file translation in InstantTranslate should be able to turn of via configuration.

Please have in mind, that maybe we will get another new feature that extends

https://jira.translate5.net/browse/TRANSLATE-471

so that overwrite by client will also take effect for TermPortal and InstantTranslate, where the settings are usually set by user and not by client.