brushes and brush engines

[emanuele at valinor.it]

I'd say:
- KisBrush -> KisBrushStamp or KisBrushTip

- KisPaintOp -> I see no reason to change this, I'd suggest  
KisPaintOperation. It can even be *not* related to brushes at all, so  
why call it KisBrushEngine or KisBrushOperation? It can represent a  
pen, a pencil, an airbrush, a china... So I'd leave it as  
KisPaintOperation, meaning that it is called from the Paint Tool to do  
a "single" operation in the "overall operation" that the tool is doing  
for the user.

- KisPaintopSettings -> KisOperationState. This class stores the state  
that the PaintOperation will use to operate, so it's an operation  
state :) I have some doubt on how and what should pass this class to  
the paint operation though... I think it's done by the paint tool.
Another problem I see in this class is that something in it is  
serializable, some other thing is not. For example: this class stores  
the actual position of the mouse, and there is no meaning in serialize  
it. But it contains the operation settings too, and those need to be  
stored... why not split this in two classes then?

- KisPaintopSettings -> KisOperationSettings, containing the  
serializable bits.
                         This class could even be loaded from the  
paintop without
                         being passed from the tool, it could read the settings
                         from a registry or something
                      -> KisOperationState. This is the information that only
                         has a sense inside the overall operation the user is
                         doing right now, and has no meaning outside it, so it
                         shouldn't be serialized. It contains the  
pointer state,
                         and some other things needed by the tool or by the
                         paintop. It preserves the information between two
                         paintop creations.

Emanuele