To prevent Warning "Trying to get property of non-object" in case when nothing set to params, but you try to get some key (check is there something)

ArrayHelper::getValue($this->view->params, 'abc');

consistent api for safe and required

when error occurs while handling errors output was not readable in web
context

adjust depended asset position or throw exception on conflict

Added Controller::enableCsrfValidation to support turning on/off CSRF validation for particular actions.

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

- cleanup API and usage, add documetation link
- introduced @property feature in getter or setter which has precedence
  over @return or @param tag if present

helps reducing weird error messages.