Add basic room upgrade support.

Add full screen image view.
Fix a bug in image provider.

imports/Spectral/Component/FullScreenImage.qml

@@ -0,0 +1,41 @@
+import QtQuick 2.12
+import QtQuick.Controls 2.12
+
+ApplicationWindow {
+    property url imageUrl
+    property int sourceWidth
+    property int sourceHeight
+
+    id: root
+
+    flags: Qt.FramelessWindowHint | Qt.WA_TranslucentBackground
+    visible: true
+    visibility: Qt.WindowFullScreen
+
+    title: "Image View - " + imageUrl
+
+    color: "#BB000000"
+
+    Image {
+        anchors.centerIn: parent
+
+        sourceSize.width: root.sourceWidth
+        sourceSize.height: root.sourceHeight
+        source: imageUrl
+    }
+
+    ItemDelegate {
+        anchors.top: parent.top
+        anchors.right: parent.right
+
+        width: 64
+        height: 64
+
+        contentItem: MaterialIcon {
+            icon: "\ue5cd"
+            color: "white"
+        }
+
+        onClicked: root.close()
+    }
+}