Title: Do not fail on non-existing Livestatus columns any longer, output None or null instead
Level: 1
Component: livestatus
Compatible: compat
Version: 1.2.7i1
Date: 1431935942
Class: feature

When you ask for a column that does not exist in your Livestatus version, now this is not
considered as a fatal error any longer but just being logged as a warning. Instead
an empty string (CSV), <tt>None</tt> (Python) or <tt>null</tt> (JSON) is being returned.
This makes it easier for GUIs to maintain compatibility with existing Livestatus version
when new features are implemented that make use of new Livestatus columns.
