Behat: New fixture notation in "manage files" tests
Behat: Support for TreeDropdownField
Behat fixture refactoring (shared factory instance)
Behat: Copy fixture identifier to "Name" or "Title" by default

This makes fixture setup less verbose, particularly for behat
tests (e.g. with "Given a page 'About Us'")
Behat: Use explicit fixtures
Merge remote-tracking branch 'origin/3.0' into 3.1

Conflicts:
	tests/behat/features/bootstrap/SilverStripe/Framework/Test/Behaviour/CmsUiContext.php