* BView::TranslateBy(), BView::ScaleBy() and BView::RotateBy()
allow to conveniently modify the current affine transformation.
This makes it unnecessary to first read the current transform,
modify it, and then set it again.
Uses the new Pre...() methods of BAffineTransform.
* Also, remove setting the transform "through" to the BView even
while recording a BPicture, as this now results in transforms
being applied more than once.