Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

**What does this do?**
It makes sure that whenever a new note is added to an noteable item, the
updated_at of that item is also updated.

**Why is this needed?**
At this moment when you post a comment on an issue or add a label to an issue,
the updated_at is not changed. Because of this the filtering for least recently
updated is not really useful (since it only takes in account the original text
from the noteable).

Signed-off-by: Jeroen van Baarsen <jeroenvanbaarsen@gmail.com>

There's a lot of code in the Note model that only deals with creating
system notes, so we're going to split that into its own class.

Having a merge request with a comments on a line which is then changed
in a later commit prevented new comments from properly showing up in the
merge request show page.

 * `Note#set_diff` do not use stored the diff when creating a new note
   in merge requests (we can not be sure the diff did not changed since
   the last comment on that line)
 * Do not rely just on `outdated?` of the first note when displaying
   comments of a MR in the discussion tab, but partition the
   active/outdated notes and display them all
 * In the inline changes tab just select the active notes, so an
   outdated note does not prevent an active one from being rendered
 * Just show active comments in the side-by-side changes tab

Fix bug where error messages from Dropzone would not be displayed on the issues page

Closes #1258

Remove emphasis from system notes to avoid Markdown conflicts in names.

This reverts commit 7602cef5.

Supports four different event types all bundled under the "note" event type:

- comments on a commit
- comments on an issue
- comments on a merge request
- comments on a code snippet

signe-in -> signed-in
go_to_gihub_for_permissions -> go_to_github_for_permissions
descendand -> descendant
behavour -> behaviour
recepient_email -> recipient_email
generate_fingerpint -> generate_fingerprint
dependes -> depends
Cant't -> Can't
wisit -> visit
notifcation -> notification
sufficent_scope -> sufficient_scope?
levet -> level

In some strange cases Ruby thinks `system` is not AR field but
Kernel.system call and raises exception during save. It should prevent
this random wierd behaviour

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

This fixes a bug where commit authors weren't receiving email notifications for notes added to their commits and their membership was in the group but not the project. The fix is to look up membership via the team object which accounts for both project and group members.

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Add a note to merge requests and issues when they're mentioned by a
merge request, issue, or commit in another project.