QmlJSEditor: Move document to its own file

Change-Id: I81c1ae5af617e801196edd612aff62ba4d864409
Reviewed-by: Eike Ziller <eike.ziller@digia.com>
QmlJSEditor: Remove unused member

Change-Id: I1a7ff8f409b535761c3a8b777febbfb0c0ed8cdd
Reviewed-by: Eike Ziller <eike.ziller@digia.com>