Set NFD logging level from GUI

refs: #2913

Change-Id: I4255b0467ef8ee6c4a2803ed078256cac9fbfd9c
diff --git a/ndn/gui.py b/ndn/gui.py
index c4097e4..653dbbc 100644
--- a/ndn/gui.py
+++ b/ndn/gui.py
@@ -48,6 +48,12 @@
         self.logLevel = StringVar(self)
         self.addDropDown("Log level:", self.logLevel, LOG_LEVELS, LOG_LEVELS[3])
 
+    def getValues(self):
+        return {
+            "log-level": self.logLevel.get()
+        }
+
+
 class NlsrFrame(GuiFrame):
 
     HYPERBOLIC_STATES = [