Re #10: Realign widgets

Now that we have top and bottom buttons, the alignment is better
if images, completion check marks and progress bars are centralised

src/widgets/AddImageButton.vala

@@ -83,14 +83,14 @@ class AddImageButton : Gtk.Button {
 
       if (draw_width > 0 && draw_height > 0) {
         ct.scale (scale, scale);
-        ct.set_source_surface (this.surface, 0, 0);
+        ct.set_source_surface (this.surface, (widget_width - draw_width) / 2 / scale, (widget_height - draw_height) / 2 / scale);
         ct.fill ();
       }
       ct.restore ();
 
       style_context.render_check (ct,
-                                  (draw_width / 2.0) - (ICON_SIZE / 2.0),
-                                  (draw_height / 2.0) - (ICON_SIZE / 2.0),
+                                  (widget_width / 2.0) - (ICON_SIZE / 2.0),
+                                  (widget_height / 2.0) - (ICON_SIZE / 2.0),
                                   ICON_SIZE,
                                   ICON_SIZE);
     }

src/widgets/ComposeImageManager.vala

@@ -169,7 +169,6 @@ class ComposeImageManager : Gtk.Container {
     bar.show_all ();
     this.progress_bars.add (bar);
 
-    // Add the progress bar first so it (should) go under the image description button
     var desc_btn = new Gtk.Button.from_icon_name("cawbird-compose-symbolic");
     desc_btn.set_parent(this);
     desc_btn.get_style_context ().add_class ("image-button");
@@ -255,7 +254,7 @@ class ComposeImageManager : Gtk.Container {
       bar.get_preferred_width (out bar_allocation.width, out n);
       bar_allocation.width = int.max (button_width - 12, bar_allocation.width);
       bar.get_preferred_height (out bar_allocation.height, out n);
-      bar_allocation.y = child_allocation.y + button_height - bar_allocation.height - 6;
+      bar_allocation.y = child_allocation.y + (child_allocation.height + bar_allocation.height) / 2;
 
       bar.size_allocate (bar_allocation);