Code was cleaned.
Corrections in removing strokes.

Corrected adding items to group.
Corrected group creation.
Corrected adding items to scene - items shouldn't be added to itemsToRemove list because that list needs for cleaning undo stack.
Improved mechanism of removing "itemsToRemove".
Removed wrong deletion of mButtons list from UBGraphicsItemDelegate destructor because that buttons has Frame as parent.
Removed possible memory leak in UBBoardController::clearUndoStack. Some items was able not deleted.
tmpScene in cffReader not deletes now because ithas a proxy as parent.

shutdown after emptying the trashbin

Fixed creation of transparent drawing view.

Mouse events handlers works for UB types and for some Qt types. Mouse events for other items hanlded by QGraphicsView.
It solves some troubles with items selections and fixes Sankore-721.

Fixed some related issues.