Non-editable content should be selected as whole when inserting.
Don't strip non-editable blocks or nested editables (less likely to happen, but still).
Added tests for inserting HTML of non-editable elements.
Updated test - now widget is selected from the very first moment.
Added test for ticket #12008.
IE8 does not support this feature.
Changelog entry.
Merge branch 't/12008' into major