Minor change to message string formatting.  Also added default to key lookups to support older (serialized) message objects.
Minor change to message string formatting.  Also added default to key lookups to support older (serialized) message objects.

git-svn-id: 56291ccb70fbcdaeccc27a45ace48359e35ec6f1@323 3e6b72d3-b629-0410-ad1b-3b4ab856adc4

jamesblunt/IbPy,blampe/IbPy,chris-ch/IbPy,chenzeyu/IbPy,sjev/ibpy,humdings/IbPy