Trackpad fixes & changes:

- UV Image editor and other 2d views didn't zoom for CTRL+swipe yet.
  (2 finger trackpad, 1 finger mighty mouse)

- Switched defaults for 3D window swiping...
  - default rotate view
  - SHIFT for translate
  - CTRL for zooms

This makes all editors use 'swipe' like 'middle mouse', and not
like scrollwheel (as in releases).

This is nice for consistancy, but it still feels a bit weird...

Of course users can config this in keymaps. We need a sensible
default though, and to make a 2D input input device behave like
middle mouse seeems more sensible than like a 1D wheel...

Proposal therefore for defaults:

- 1D scrollwheels: zoom in 3d, zoom in 2d, but scroll for list views.

- 2D trackpads: pan for all 2d views, rotate for 3D

I'll check with frequent trackpad users about this and we can freeze it
before release. Give it a try :)

source/blender/editors/space_image/image_ops.c

@@ -457,7 +457,7 @@ enum {
 
 static int image_view_zoom_invoke(bContext *C, wmOperator *op, wmEvent *event)
 {
-	if (event->type == MOUSEZOOM) {
+	if (event->type == MOUSEZOOM || event->type == MOUSEPAN) {
 		SpaceImage *sima = CTX_wm_space_image(C);
 		ARegion *ar = CTX_wm_region(C);
 		float delta, factor, location[2];