Graphics tools: Fix goBack, showOption and delete actions

[chgans]

Move goBack and possibly showOption from AbstractGraphicsInsertTool to AbstractGraphicsInteractiveTool
This will allow the select tool to manage at least the "go back" action: cancel current operation (item move, clone, handle move)
Not sure showOption is needed for the selectTool, so maybe optionDialog need to be moved instead from GraphicsTool to AbstractGraphicsInsertTool, since non interactive tool are not... interactive!
Delete action is not implemented, but basically just pressing delete should:

• delete selected items or current moving items
• delete (if supported) the current moving handle