Updated mediawiki/extensions
Project: mediawiki/extensions/DataValues  9788bf927155c13cf4b94a1bf9714a6bf5d74b4a

valueview experts have a clear definition of destroy now

- documented destroy properly, removed related TODOs
- implemented missing destroy methods
- added tests for destroy to testExpert and improved some other existing tests

Change-Id: I634c67b27e30f3b8d3a3202f1908b9752aded7a3