Silently resolve redirects via EntityLookup

WikibaseRepo and WikibaseClient now provide EntityLookup
instances that silently resolveone level of redirects.

Redirects will thus Just Work in many places.

Code that uses EntityRevisionLookup should be surveyed
as to whether it should or should not resolve redirects.
Generally, any code related to editing should not.

Bug: 66075
Change-Id: I0e50fcc4536751e941334810d73de0c87de0cda6