Updated mediawiki/extensions
Project: mediawiki/extensions/Flow  967ac4f27d8352433f09ef01f976ed710e85ba9b

Add diff view of changes to board header

Dependent changes involved:

* Handling of new custom blocks
* Report error on unrecognized actions
* Refactor post diff code to be re-used for header diff
* Add board header diff view

Change-Id: I363b6bd9e972467953b0e64cd437309ce08446b7