remove unused code
 create class PencilTool
PenTool: add Q_OBJECT macro
ScribbleArea: move filed 'pencil' to PencilTool
create class BrushTool
ToolType: rename COLOURING => BRUSH
ScribbleArea: move brush init code into BrushTool
minor
BrushTool: fix compile error
BrushTool: return type code
ScribbleArea: move filed 'brush' to BrushTool
EraserTool: create class
ScribbleArea: fix compile error, this brush is not that bursh
ScribbleArea: move Eraser init code into EraserTool
ScribbleArea: move Properties 'eraser' to EraserTool
minor
ScribbleArea: fix bug, app crash after switch tool Pen 2 times,.
Property: pressure etc.. type change from bool to int,
they has 3 states, 1=on 2=off -1=disabled,
ScribbleArea: this line let app crash, why?
last commit is a mistake. fix it now.