QT: Implement themed icons (#3554)

* implement themed icons

* fix theme search paths

dist/qt_themes/default/default.qrc

@@ -0,0 +1,11 @@
+<RCC>
+    <qresource prefix="icons/default">
+        <file alias="index.theme">icons/index.theme</file>
+      
+        <file alias="16x16/checked.png">icons/16x16/checked.png</file>
+
+        <file alias="16x16/failed.png">icons/16x16/failed.png</file>
+      
+        <file alias="256x256/citra.png">icons/256x256/citra.png</file>
+    </qresource>
+</RCC>

dist/qt_themes/default/icons/index.theme

@@ -0,0 +1,10 @@
+[Icon Theme]
+Name=default
+Comment=default theme
+Directories=16x16,256x256
+ 
+[16x16]
+Size=16
+ 
+[256x256]
+Size=256

dist/qt_themes/qdarkstyle/icons/index.theme

@@ -0,0 +1,11 @@
+[Icon Theme]
+Name=qdarkstyle
+Comment=dark theme
+Inherits=default
+Directories=16x16,256x256
+ 
+[16x16]
+Size=16
+ 
+[256x256]
+Size=256

dist/qt_themes/qdarkstyle/style.qrc

@@ -1,4 +1,7 @@
 <RCC>
+  <qresource prefix="icons/qdarkstyle">
+    <file alias="index.theme">icons/index.theme</file>
+  </qresource>
   <qresource prefix="qss_icons">
     <file>rc/up_arrow_disabled.png</file>
     <file>rc/Hmovetoolbar.png</file>