Organize project files

Put QML components into folders, remove unused ones, split __init__.py
with engine.py.

harmonyqml/components/chat/MessageList.qml

@@ -0,0 +1,24 @@
+import QtQuick 2.7
+import QtQuick.Controls 2.2
+import QtQuick.Layouts 1.4
+
+Rectangle {
+    property int space: 8
+
+    Layout.fillWidth: true
+    Layout.fillHeight: true
+    Layout.leftMargin: space
+    Layout.rightMargin: space
+
+    ListView {
+        id: messageListView
+        anchors.fill: parent
+        model: Backend.messagesModel[chatPage.room.room_id]
+        delegate: MessageDelegate {}
+        //highlight: Rectangle {color: "lightsteelblue"; radius: 5}
+
+        clip: true
+        topMargin: space
+        bottomMargin: space
+    }
+}