removed getPostParam() from Request, body is $_POST by default

fixes #2093
adjusted changeloadjusted changelogg
Merge pull request #2181 from cebe/request-body-default-post-params

removed getPostParam() from Request, body is $_POST by default
Added `yii\web\Request::get($name = null, $defaultValue = null)` and `yii\web\Request::post($name = null, $defaultValue = null)`
Fixed an issue with Filehelper and not accessable directories

which resulted in endless loop

http://www.yiiframework.com/forum/index.php/topic/50982-cfilehelper-bug-security-flaw/