*	The grid drawing code has been factored out to a separate helper class.
	The parameters of the grid are now stored within the class, which facilitates passing them around.
	Now we can have as many grids as we please.
*	The grids are being prepared in the circuit view's constructor, so we don't need to recreate them from scratch on every drawing.
	In the Erase event, we can simply draw them.
*	Now we can draw the grid with an offset.
	This will be useful when drawing the grid inside damaged regions only.
	We can then start from the left-top corner of the visible rectangle,
	add the offset to get the coordinates of the first line, and start drawing from there.

TODO
*	Limit drawing the grid to the damaged regions only.