added possibility to define global and local log levels

lib/log4js.js

@@ -265,14 +265,25 @@ function LoggingEvent (categoryName, level, message, exception, logger) {
  */
 function Logger (name, level) {
     this.category = name || DEFAULT_CATEGORY;
-    this.level = Level.toLevel(level, levels.TRACE);
+
+    if (! this.level) {
+        this.setLevel('TRACE');
+    }
 }
 sys.inherits(Logger, events.EventEmitter);
 
 Logger.prototype.setLevel = function(level) {
+    this.__proto__.level = Level.toLevel(level, levels.TRACE);
+};
+
+Logger.prototype.setLocalLevel = function(level) {
     this.level = Level.toLevel(level, levels.TRACE);
 };
 
+Logger.prototype.removeLocalLevel = function() {
+    delete this.level;
+};
+
 Logger.prototype.log = function(logLevel, message, exception) {
     var loggingEvent = new LoggingEvent(this.category, logLevel, message, exception, this);
     this.emit("log", loggingEvent);