Improve Visibility of Commit Comments

It's difficult to see and find commit comments in Stash. Comments can only be found by getting the notification email or manually navigating to the commit in Stash.

1. Create a comment notification inbox similar to the current pull request inbox
   1. Show recent and unread comments in the inbox and provide a quick link to see the comment in the code
2. Provide an overview page that shows all comments for a commit
   1. Show the comment and a snippet of code surrounding it to make it easier to see all comments in a commit
   2. The current comment icon with a count on the commits listing page could link here