Currently comments on commits and merge requests do not require merge request- or commit-specific information, but can use the same template. Rather than change the method which calls the template, I opted to keep the templates separate and create a new template to highlight their identicality, while preserving the option to distinguish them from each other in the future.

Also removed some of the inconsistencies between text and html email versions.

Still needed is a text-only version of git diffs and testing.

* upstream/master: (70 commits)
  Fix routing spec for group controller
  Add small improvements to constrainers and specs
  Faster search
  Fix broken commits search
  Changed helper method to check for none on params Moved if statements around in view
  API: Return 400 when creating a systemhook fails
  Update non-exist group spinach test to match routing
  Bump omniauth-gitlab to 1.0.2 to fix incompatibility with omniauth-oauth2
  Replace trigger with the new ID of the docs project
  Refactor method name
  17492 Update link color for more accessible contrast
  Fixed todos empty state when filtering
  Refactor namespace regex
  implements reset incoming email token on issues modal and account page, reactivates all tests and writes more tests for it
  Use separate email-friendly token for incoming email and let incoming email token be reset
  Use the Gitlab Workhorse HTTP header in the admin dashboard
  Refactor project routing
  Fix 404 when visit /projects page
  Rewritten spinach git_blame tests to rspec feature tests
  Add tests for project#index routing
  ...

We use bcc here because we don't want to generate this emails for a
thousand times. This could be potentially expensive in a loop, and
recipients would contain all project watchers so it could be a lot.

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6019#note_16963209

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6019#note_16956802