Jetpack Likes

Abstracted the like count code (for wp-admin post page) out so Jetpack and WordPress.com can overwrite them on a per-need basis. This does not change how Jetpack likes or the post count code works in JP functionally.
props beaulebens


git-svn-id: https://plugins.svn.wordpress.org/jetpack/trunk@759380 b8457f37-d9ea-0310-8a92-e5e31aec5664