WIP Use ChangeOps consistently throughout API

Authored by WMDE-leszek on Apr 19 2018, 1:26 PM.

Description

WIP Use ChangeOps consistently throughout API

Avoid redundant implementations in dedicated Lexeme API endpoints and
ChangeOps used when executing request through wbeditentity.

Bug: T190928
Depends-On: Ifcb72f5f88e0c02dd404ec6bb043520df5e0ea9e
Depends-On: I5be06540e2ba4c28bb37afa425456f754ee33b67
Change-Id: I5913ae91255f87613742e13299df43aedba1f763