==Sequencer==

Added patch by Matt Ebb, that enhances the sequencer GUI in several ways:
- It looks a lot better
- Strip colours are themeable.
- The drawing code is more readable.
- The background of the timeline makes now distinguishing the channels easier
  by alternating between different shades of gray.
- Handle-scaling is clamped to min and max-values, making it possible to
  grab strips at large zooming levels more easily.
- Preview-images can be panned by dragging it with the middle mouse button.
  Home-Key resets the position.
- Since some people can't grab the meaning of "C 0", it is renamed to "Chan: 0"
- Effect strips have slightly different colors to distinguish them better.

Additionally:
- fixed an off by one error in Matt's patch
- Scene-rendering saves CFRA to avoid jumping current-scene on scrub
  (might be academic fix, since most likely it only happens if you add
  the sequencer-scene to the timeline... But nevertheless it bugs you on
  testing the GUI ;-)

source/blender/src/interface_draw.c

@@ -188,10 +188,10 @@ static void ui_draw_icon(uiBut *but, BIFIconID icon)
 			xs= but->x1+1.0;
 		}
 		else if ((but->type==ICONROW) || (but->type==ICONTEXTROW)) {
-			xs= but->x1+4.0;
+			xs= but->x1+3.0;
 		}
 		else {
-			xs= but->x1+6.0;
+			xs= but->x1+4.0;
 		}
 		ys= (but->y1+but->y2- height)/2.0;
 	}