Related to previous commits. A minor final change to have rudimentary support for GS3 interface translations in the online GTI system. The current change just says that a GS2 server can't show you GS3 interface translations in action. Together with previous commits, now files can be downloaded for offline translating. This is unchecked in Microsoft spreadsheet, but the file looks okay to the eye. Adding translations via the local GTI seems to work as it ends up in the correct properties file. But have not checked whether offline spreadsheets when returned from translators can be successfully processed by Greenstone code. This is in case spreadsheet processing for GS3 works differently, since there are multiple interface files for one module, whereas for GS2 each module corresponds to a single interface file.