Added 'getExtensionByMimeType' method to CFileHelper class, enh #3513
Merge branch 'master' of git://github.com/yiisoft/yii into 3513-added-getExtensionByMimeType-method-to-CFileHelper
Populated 'fileExtensions.php' file
Merge pull request #3516 from ua2004/3513-added-getExtensionByMimeType-method-to-CFileHelper

Added 'getExtensionByMimeType' method to CFileHelper class, enh #3513