Html::setTitle() should be in a separate extension

[antick]

Skyii uses Html::setTitle() method for setting up title in the html head tag.

Right now this method is created in common helpers. Think we need to put this in a separate extension which can be called as skyii helpers or something like that. This custom helper will extend the Yii helpers and a user can extend the skyii helpers to create his own.

Need to document it properly once it's done.