Enforce some type hinting in Linker class

Specifically for link(), linkText(), makeImageLink(),
and makeBrokenImageLinkObj() functions

Change-Id: I4c397de289ae51bc463b5ae7c2968703d1424368
Change MediaWiki UI to use skinStyles so skins can customize

Bug: 70351
Change-Id: I5d5725dba7e8e65b8fe3f5213b5e50d8dfeba755
Merge "Enforce some type hinting in Linker class"
Merge "Change MediaWiki UI to use skinStyles so skins can customize"