This patch implements:

1) KisImage::requestProjectionUpdateNoFilthy() the same as layer->setDirty(),
   but skips regeneration of layer's projection.

2) KisLayer::updateProjection() now accepts not layer's position, but
   a pointer to the filthy node.

3) KisEffectMask::decorateRect() now accepts a position relative to the
   filthy mask/layer calculated inside the layer itself. *Not* the one used
   by KisAsyncMerger.

Known bugs: tested only with affine transformations, that is Free and
            4-point perspective