Client: add qt-based client (initial commit)

Author: fuzun

client/qt/assets/assets.qrc

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+<RCC>
+    <qresource prefix="/">
+        <file>bgImages/dark.jpg</file>
+        <file>bgImages/light.jpg</file>
+        <file>icons/Camera.svg</file>
+        <file>icons/Log.svg</file>
+        <file>icons/Settings.svg</file>
+        <file>icons/About.svg</file>
+        <file>bgImages/license.txt</file>
+        <file>icons/license.txt</file>
+        <file>icons/Message.svg</file>
+        <file>icons/Shutdown.svg</file>
+        <file>icons/Error.svg</file>
+        <file>icons/Information.svg</file>
+        <file>icons/Warning.svg</file>
+        <file>icons/Statistics.svg</file>
+        <file>icons/built-with-qt.png</file>
+    </qresource>
+</RCC>

client/qt/assets/bgImages/dark.jpg

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+All images are used under Pexels License (https://www.pexels.com/license).
+* dark.jpg file contains "Northern Lights" photo photographed by "stein egil liland" which was available at (https://www.pexels.com/photo/northern-lights-1933319).
+* light.jpg file contains "Landscape Photo of Mountain Filled With Snow" photo photographed by "eberhard grossgasteiger" which was available at (https://www.pexels.com/photo/landscape-photo-of-mountain-filled-with-snow-1004665).