issue: standard error messages

[Robert Sayre <mint@xxxxxxxxxxxxxxx>]

I've noticed that TypePad sends human readable error messages in the 
message body like this:

<error>Hey, you screwed up</error>

Should we standardize that? Maybe, but someone might want to extend the 
protocol with additional information.

How about

<error>
	<description>Hey, you screwed up</description>
</error>

or maybe

<error>
	<item>
		<title>Application Error</title>
   		<description>blah blah</description>
        </item>
</error>

Robert Sayre