* Add a new hook 'register_account_menu_item'
This new hook makes it easier for third party apps to add new buttons on
the 'my account' page in the Wagtail admin. Existing buttons are
converted to the new hooks to make the code consistent.
* Add documentation for the new register_account_menu_item hook
(technically we should standardise on no leading space, because the leading space creates a blockquote element - however, it's not really noticeable in the end result, and this way we can easily copy and paste from the changelog...)
* Fix incorrect assertion in TestSystemCheck
It only worked by accident, due to the definition of equality on block objects.
* Explicitly cast child_blocks.items() to a list when deconstructing blocks
The result of items() is a lazily-evaluated ItemsView object, which Django's deep_deconstruct function (used to detect changes for migrations) doesn't recognise; as a result, the blocks inside it don't get deconstructed. Luckily, this doesn't break migration change detection, because we define __eq__ on Block so that two blocks with matching definitions are considered equal. Nevertheless, it's best that we don't rely on that behaviour; it was only implemented originally as a workaround for https://code.djangoproject.com/ticket/24340 in Django <1.9 (where deep_deconstruct didn't recurse into lists either).
* Bring comment for Block.__eq__ up to date
* Issue 4334: Excluded fields are also excluded when a panel set is explicitly defined on a model.
* Improved notation after review with @BertrandBordage
* Incorrect field name in comment
I'd like to propose removing the shims for IE6-9 from the project template.
The rationale for this is the same as for dropping support for EOL version of Django, etc. - i.e., these versions of Internet Explorer are no longer supported by the vendor (the last version of Windows that you cannot upgrade to use IE10 or higher was Windows XP, which reached end of life in 2014).
On that basis I think that Wagtail should not include these shims by default - projects that for whatever reason still need to support these browsers can easily add them to their templates.