Started CKEditor 4.5 development.
Implemented nested widgets destroying on nestedEditable.setData and extended related repository methods.
Check that wrapper has not been detached from DOM in the meantime.
Ported tests for widgets garbage collection from CKTester.
Mentioned nested widgets in modified methods.
Merge branch 't/12018' into major
Merge branch 'master' into major

Conflicts:
	dev/builder/build.sh
Merge branch 'master' into major
Merge branch 'master' into major
Uncommented test disabled in #12054 on master.
Allowed block widgets to be dragged and dropped in nested editables.
Check nested editable filter to make sure widget can be dropped there.
Don't let the widget to be dropped into its own nested editable.
Tests: Extracted lineutils tools with lineutilsTestsTools#assertRelations method.
Tests: Added test for dropping widgets into nested editable of restricted filter.
Tests: Added tests for widget drop into nested editables: of no specific filter and own nested editable. Minor test refactoring.
Changelog entry.