Update git submodules
- Update extensions/MultimediaViewer from branch 'REL1_39' to 3890f0f176d094de8062f24a413f9377b592672a
- Localisation updates from https://translatewiki.net.
Change-Id: I27311f7b5ec1b44584f3edc62cb51dd84245ee9b
- Localisation updates from https://translatewiki.net.