added note about setVariable argument

Author: Will Witman

docs/javadocs-javacallout/com/apigee/flow/message/MessageContext.html

@@ -413,7 +413,7 @@ <h4>setVariable</h4>
 <dl>
 <dt><span class="paramLabel">Parameters:</span></dt>
 <dd><code>name</code> - The name of the flow variable.</dd>
-<dd><code>value</code> - The new value for the variable.</dd>
+<dd><code>value</code> - The new value for the variable. The item is set as an object, and not flattened upon insertion.</dd>
 <dt><span class="returnLabel">Returns:</span></dt>
 <dd>true if the variable was set;
          false if the variable is read-only or if it does not exist.</dd>