Update git submodules
- Update extensions/MultimediaViewer from branch 'REL1_40' to c2ef6e02a74d502497308d828a64d05156cff50b
- Localisation updates from https://translatewiki.net.
Change-Id: I0f7519769398427d26e39c28e662b9fb0ab94c38
- Localisation updates from https://translatewiki.net.