Adds the ability to specify the view class used by the outlet Handlebars helper

Previous to this change, the view class used was always an "OutletView" (Metamorph extension of ContainerView).  This change allows the class to be set while still defaulting to the OutletView
Merge pull request #2310 from robharper/feature/outlet-viewclasses

Ability to specify the view class used by the outlet Handlebars helper