Allow QGraphicsTextItem to not ensure visibility

When QGraphicsTextItem receives focus or its text is modified, it ensures item is visible in all QGraphicsViews as documented here: http://doc.qt.io/qt-5/qgraphicstextitem.html#setPlainText

This can be troublesome especially for UIs which use multiple QGraphicsViews for a single UI component. For example Qt 3D Studio timeline currently contains hack to disable this behavior by overriding QGraphicsView::scrollContentsBy() as seen here http://code.qt.io/cgit/qt3dstudio/qt3dstudio.git/tree/src/Authoring/Studio/Palettes/TimelineGraphicsView/ui/TreeHeaderView.cpp

But if you want to disable this behavior while keeping rest of scrolling behavior, things become more complicated. There should be a cleaner way to avoid QGraphicsTextItem not causing ensureVisibility or QGraphicsView not reacting to these.