<LinkedForm> tag now only added to XML if there's a value

Change-Id: I2b061f3266c3ea367eb6fb689f69706a0a9b1c0a
Localisation updates from https://translatewiki.net.

Change-Id: Ia6c54323ec85765384537c3a16b124b8f00a0cb0
Localisation updates from https://translatewiki.net.

Change-Id: I2409e7cee8a35626dd539e11b5c83aaa0848bf16
Localisation updates from https://translatewiki.net.

Change-Id: I875709108d6f8e28157a474b3e3d7fb99fe562d8
Localisation updates from https://translatewiki.net.

Change-Id: I8c2ef8351c7ef56a9727f81928bf2e2099a6023d
Merge branch 'master' of ssh://wmfgerrit/mediawiki/extensions/SemanticMediaWiki