Error Tracking allows GitLab to receive and act on application errors. We should improve the workflow between GitLab and Sentry, to allow users to more easily work with and interact with errors. We should: * Allow users to configure a Sentry project to a GitLab project (URL, token) * List the errors for their project * View the key details of an error This will lay the foundation to allow us to also embed errors within an Issue and Merge Requests, as well as additional features for determining analytics around the cause of an error. Sentry has also started adding source code awareness: https://blog.sentry.io/2017/05/01/release-commits.html