[ui] Controls: add Group custom control

meshroom/ui/qml/Controls/Group.qml

@@ -0,0 +1,47 @@
+import QtQuick 2.7
+import QtQuick.Controls 2.3
+import QtQuick.Layouts 1.3
+import MaterialIcons 2.2
+
+/**
+ * A custom GroupBox with predefined header.
+ */
+GroupBox {
+    id: root
+
+    title: ""
+    property int sidePadding: 6
+    property alias labelBackground: labelBg
+    property alias toolBarContent: toolBar.data
+
+    padding: 2
+    leftPadding: sidePadding
+    rightPadding: sidePadding
+    topPadding: label.height + padding
+    background: Item {}
+
+    label: Pane {
+        background: Rectangle {
+            id: labelBg
+            color: palette.base
+            opacity: 0.8
+        }
+        padding: 2
+        width: root.width
+        RowLayout {
+            width: parent.width
+            Label {
+                text: root.title
+                Layout.fillWidth: true
+                elide: Text.ElideRight
+                padding: 3
+                font.bold: true
+                font.pointSize: 8
+            }
+            RowLayout {
+                id: toolBar
+                height: parent.height
+            }
+        }
+    }
+}

meshroom/ui/qml/Controls/qmldir

@@ -1,4 +1,5 @@
 module Controls
 
 FloatingPane 1.0 FloatingPane.qml
+Group 1.0 Group.qml
 MessageDialog 1.0 MessageDialog.qml