Block Level Sharing in Galleries

![screen shot 2014-10-17 at 15 46 01](https://cloud.githubusercontent.com/assets/2236852/4680607/58efe2a0-560c-11e4-9c7e-233e8f4230e9.png)

1. Refactored block level sharing to abstract code for use on galleries and other content types in the future
2. Block level sharing is now available in galleries, including lightbox mode
I's check with @cantlin if any of these urls need campaign tracking codes on them too.