Remove dependency on Qt in qrenderdoc python module

* The main addition here apart from some extra stubs is a new rdc type
  for date time objects.
* Although the module doesn't do anything and is only used for docs
  reflection it is desirable to not have to link against Qt as this
  can cause problems when linking the module without unresolved symbols.

qrenderdoc/Code/pyrenderdoc/PythonContext.cpp

@@ -917,3 +917,13 @@ extern "C" void SetThreadBlocking(PyObject *global_handle, bool block)
   if(redirector && redirector->context)
     return redirector->context->setThreadBlocking(block);
 }
+
+extern "C" QWidget *QWidgetFromPy(PyObject *widget)
+{
+  return PythonContext::QWidgetFromPy(widget);
+}
+
+extern "C" PyObject *QWidgetToPy(QWidget *widget)
+{
+  return PythonContext::QWidgetToPy(widget);
+}