Fixed the issue that Object/Component doesn't support using anonymous function as normal property values.

this allows implementing __call() in behaviors

See this forum topic for details:
http://www.yiiframework.com/forum/index.php/topic/46629-invoke-behavior-method-through-php-magic-method-call-dosent-work/

return false, not null

Need to add ensureBehaviors() to detachBehavior*().

The intent may be to detach behaviors defined in behaviors().
In the original implementation, if these behaviors() are not yet attached, they can not selectively be detached.

added more exception classes.
working on request and response classes.

Finished ExpressionDependency.