Pinterest sharing in galleries

Galleries now have the option of block level and page level Pinterest sharing. 

This required the addition of extra Facebook open graph tags to ensure high resolution images were picked up by the Pinterest scraper.

![screen shot 2014-10-31 at 17 06 57](https://cloud.githubusercontent.com/assets/2236852/4881174/bbfc4348-6345-11e4-965e-23f08882ef17.png)

![screen shot 2014-10-31 at 17 07 02](https://cloud.githubusercontent.com/assets/2236852/4881176/c16ec15c-6345-11e4-9323-fa1d660239ba.png)

![screen shot 2014-10-31 at 17 07 09](https://cloud.githubusercontent.com/assets/2236852/4881182/c66dd080-6345-11e4-9c73-b3c154cffd91.png)