misc: removed debug print, added info for missing icons

- Added description to the Icons() util, to describe why it's useful
(#998).

ui/opensnitch/dialogs/ruleseditor.py

@@ -223,7 +223,6 @@ class RulesEditorDialog(QtWidgets.QDialog, uic.loadUiType(DIALOG_UI_PATH)[0]):
         self.selectNetsListButton.setEnabled(state)
 
     def _cb_uid_combo_changed(self, index):
-        print(index, "uid:", str(self._users_list[index][self.PW_UID]))
         self.uidCombo.setCurrentText(str(self._users_list[index][self.PW_UID]))
 
     def _set_status_error(self, msg):

ui/opensnitch/utils/__init__.py

@@ -432,8 +432,10 @@ class NetworkServices():
         return self.ports_list.index(str(port))
 
 class Icons():
-    """
-    https://www.pythonguis.com/faq/built-in-qicons-pyqt/icons-builtin.png
+    """Util to display Qt's built-in icons when the system is not configured as
+    we expect. More information:
+        https://github.com/evilsocket/opensnitch/wiki/GUI-known-problems#no-icons-on-the-gui
+        https://www.pythonguis.com/faq/built-in-qicons-pyqt/icons-builtin.png
     """
 
     defaults = {