Change default logging level for XEngine to WARN instead of DEBUG.

This is to reduce log spam from script loading, which is especially spammy for avatar movements with scripted attachments.
All important messages are at warn or above.
If you still want/need to see these messages, set <level value="DEBUG"/> in the <logger name="OpenSim.Region.ScriptEngine.XEngine"> section of OpenSim.exe.config.
This affects no other package logs, which still output at the root configured level (currently DEBUG by default).

bin/OpenSim.exe.config

@@ -31,5 +31,10 @@
       <appender-ref ref="Console" />
       <appender-ref ref="LogFileAppender" />
     </root>
+
+    <logger name="OpenSim.Region.ScriptEngine.XEngine">
+      <level value="WARN"/>
+    </logger>
+
   </log4net>
 </configuration>