Merge commit '91e286^' into 19-to-1x

Conflicts:
	docs/guides/hooks-list.rst
	engine/classes/ElggInstaller.php
	engine/classes/ElggMenuItem.php
	engine/classes/ElggUpgrade.php
	engine/lib/languages.php
	engine/lib/navigation.php
	engine/lib/relationships.php
	engine/lib/users.php
	engine/tests/phpunit/ElggUpgradeTest.php
	views/default/css/admin.php