Metadata display support - patch by Julian and me.

Basically, blender adds a few metadata fields to images when
we render an image. Those metadata can now be viewed in the
image editor.

Also, made sure metadata are available when we write imbufs
to disc with "Save As". There may be more cases here that need
fixing, but this means that loading an image with metadata
will now properly preserve them in blender.

release/scripts/startup/bl_ui/space_image.py

@@ -84,6 +84,7 @@ class IMAGE_MT_view(Menu):
             layout.prop(toolsettings, "show_uv_local_view")
 
         layout.prop(uv, "show_other_objects")
+        layout.prop(uv, "show_metadata")
         if paint.brush and (context.image_paint_object or sima.mode == 'PAINT'):
             layout.prop(uv, "show_texpaint")
             layout.prop(toolsettings, "show_uv_local_view", text="Show same material")