Update git submodules
- Update extensions/MultimediaViewer from branch 'REL1_42' to 7f6f7ece56dd32b27c9c139e0287961f9d58ac3e
- Localisation updates from https://translatewiki.net.
Change-Id: I8fa9a768bcb26d4c61bdfd9c00b3111fcf93d252
- Localisation updates from https://translatewiki.net.