get opengraph site type from settings, else from the applicationcontroller
set a default for site type if it is not defined
use a default for the site type if one has not been set in settings, or in controller
improve name of opengraph object type variables
fix typo in opengraph meta
correctly handle multiple values of an opengraph tag
allow for custom open graph tags to be set
use a simple selector for getting open graph images
opengraph images require absolute urls
neaten up tag generation