Rotobrush freezing improvements

Two quick suggestions to improve rotobrush, especially for projects that are using it a lot.

1) Have an indication in the Effects Controls panel to show if the rotobrush has been frozen or not.  This makes it easier to see if a layer is frozen without having to open the rotobrush in the layer window

2) Be able to queue up / batch freeze multiple rotobrush layers, preferably in the background. A sort of "render queue" but for rotobrush layers...