Add getLogger() to IServerContainer

Makes my IDE complaining less ;-)

lib/public/iservercontainer.php

@@ -214,6 +214,13 @@ interface IServerContainer {
 	 */
 	function getJobList();
 
+	/**
+	 * Returns a logger instance
+	 *
+	 * @return \OCP\ILogger
+	 */
+	function getLogger();
+
 	/**
 	 * Returns a router for generating and matching urls
 	 *