DisplaySettings: Give the UI a facelift :^)

- Split the main UI into two tabs: "Background" and "Monitor".
- Use a GUI::IconView for selecting background pictures.
- Tweak layout, spacing, etc.

Userland/Applications/DisplaySettings/BackgroundSettings.gml

@@ -0,0 +1,77 @@
+@GUI::Widget {
+    fill_with_background_color: true
+
+    layout: @GUI::VerticalBoxLayout {
+        margins: [8, 8, 8, 8]
+    }
+
+    @DisplaySettings::MonitorWidget {
+        name: "monitor_widget"
+        fixed_width: 304
+        fixed_height: 201
+    }
+
+    @GUI::Widget {
+        fixed_height: 20
+    }
+
+    @GUI::Label {
+        shrink_to_fit: true
+        fixed_height: 16
+        text_alignment: "CenterLeft"
+        text: "Select a background picture:"
+    }
+
+    @GUI::Widget {
+        layout: @GUI::HorizontalBoxLayout {
+            spacing: 8
+        }
+
+        @GUI::IconView {
+            name: "wallpaper_view"
+        }
+
+        @GUI::Widget {
+            shrink_to_fit: true
+
+            layout: @GUI::VerticalBoxLayout {
+            }
+
+            @GUI::Button {
+                name: "wallpaper_open_button"
+                tooltip: "Select wallpaper from file system."
+                text: "Browse..."
+                shrink_to_fit: true
+            }
+
+            @GUI::Widget {
+                fixed_height: 12
+            }
+
+            @GUI::Label {
+                text: "Mode:"
+                text_alignment: "CenterLeft"
+                fixed_height: 16
+            }
+
+            @GUI::ComboBox {
+                name: "mode_combo"
+            }
+
+            @GUI::Widget {
+                fixed_height: 12
+            }
+
+            @GUI::Label {
+                text: "Color:"
+                text_alignment: "CenterLeft"
+                fixed_height: 16
+            }
+
+            @GUI::ColorInput {
+                name: "color_input"
+                fixed_width: 90
+            }
+        }
+    }
+}