add removeCommand function

lib/ace/commands/command_manager.js

@@ -20,6 +20,22 @@ var CommandManager = function(commands) {
             this._buildKeyHash(command);   
         }
     };
+    
+    function removeCommand(command) {
+        var name = (typeof command === 'string' ? command : command.name);
+        command = this.commands[name];
+        delete commands[name];
+
+        // exaustive search is a little bit brute force but since removeCommand is
+        // not a performance critical operation this should be OK
+        var ckb = this.commmandKeyBinding;
+        for (var hashId in ckb) {
+            for (var key in ckb[hashId]) {
+                if (ckb[hashId][key] == command)
+                    delete ckb[hashId][key];
+            }
+        }
+    };
 
     var platform = useragent.isMac ? "mac" : "win";