Add a project explorer to the python scripting window

* This displays the current UI extension files, some built-in examples, and
  recently opened loose files

qrenderdoc/Windows/PythonShell.ui

@@ -436,6 +436,19 @@
     </rect>
    </property>
   </widget>
+  <widget class="RDTreeWidget" name="projectExplorer">
+   <property name="geometry">
+    <rect>
+     <x>540</x>
+     <y>40</y>
+     <width>161</width>
+     <height>141</height>
+    </rect>
+   </property>
+   <property name="frameShape">
+    <enum>QFrame::NoFrame</enum>
+   </property>
+  </widget>
  </widget>
  <customwidgets>
   <customwidget>
@@ -453,6 +466,11 @@
    <extends>QTextEdit</extends>
    <header>Widgets/Extended/RDTextEdit.h</header>
   </customwidget>
+  <customwidget>
+   <class>RDTreeWidget</class>
+   <extends>QTreeWidget</extends>
+   <header>Widgets/Extended/RDTreeWidget.h</header>
+  </customwidget>
  </customwidgets>
  <resources>
   <include location="../Resources/resources.qrc"/>