Move special page code out of Lib

This moves SpecialWikibaseQueryPage and SpecialWikibasePage out of lib.

There was one page in Client using those, which now got the code inlined.
After inlining it, further refactoring was done to remove now not needed complexity.

Change-Id: I5b3e76af8b29e9da4a392e42f3dc9c2016fbf04f
Merge "Move special page code out of Lib"