Heavy update to the compositor

I think the Blender compositor could be a fantastic tool, but it's really neglected and it needs a heavy update. Here are my suggestions for just some basics:

• starting with some playback buffering - as it's not even possible to play an image sequence
• There should also be an easy way of previewing the node graph at any node, and quickly switching between different views
• bounding box/canvas should expand if some effects go beyond the image resolution
• a normal premult/unpremult workflow
• ability to switch between RGBA channels with key shortcuts for Backdrop preview
• possibility to switch Backdrop resolution to proxy, like 1:2, 1:4, for faster previews
• in the Shift+A Add node menu it should be possible to start typing the tool name without clicking on the search button
• Compositing layout with Backdrop in a new window - for Dual screen setup
• gain & gamma controls for the Backdrop preview