Update git submodules
- Update extensions/MultimediaViewer from branch 'REL1_40' to 7351793436c59d43a7f855d50e9c7a8ede82f6a7
- Localisation updates from https://translatewiki.net.
Change-Id: I9c994d847a0f9c0399d1ffc9012084836c19c681
- Localisation updates from https://translatewiki.net.