Include decent social metadata

[Igor Santos]

Currently all pages are displaying the Sugar Loaf icon as image on Facebook!

• include default metadata for Twitter, Facebook, G+ and Search Engines
• include custom metadata for pages such as search, event, theme, profile

Using sections could be a great way to achieve this, but I'm not sure how we could have default values for sections? maybe @section('desc') xxxx @endsection would do?