Fix issues in Entity::patch

* The base claim list passed in did not have claim guids as keys
* The MapPatcher comparison behaviour was not altered to behave correctly for Claim objects

This change depends on https://gerrit.wikimedia.org/r/#/c/60870/

Change-Id: I86d158e9653724c36575d93952da9317fca0f349
Merge "Fix issues in Entity::patch"