added doc to registerMetaTag()
added doc to registerMetaTag()

git-svn-id: 61b9b1e8143c05117000ae2af61f2b96f35cce2f@3231 c7f931c7-7552-0410-b027-2fb3d89d9100

dmtrs/unofficial-yii-framework-mirror,dmtrs/unofficial-yii-framework-mirror,dmtrs/unofficial-yii-framework-mirror