Pass the revid when expanding templates

 * Adds support {{REVISIONID}} and similar variables.

 * Depends on the upstream patch being deployed,
   https://gerrit.wikimedia.org/r/#/c/176305/

Bug: T73306
Change-Id: I2396709a93c42e951b3d0ef2ba054924efbf3c43
Merge "Pass the revid when expanding templates"