Don't send an email for "mentioned in" notes

Currently, an email is sent every time a mentionable is referenced by an issue, a commit or a merge request: if I comment "This MR is related to #5", the watchers get one email for the comment, and another one stating "Issue #5 was mentioned by issue #13".

This is annoying — but the biggest issue is when pushing an existing branch. Every issue referenced by commit messages in this branch will get a new mention (which is fine), and dozens of emails will be sent for all these new mentions (which is not).

This commit fixes the spam by avoiding to send an email when a new mention is added to an existing mentionable. In most cases the email notification sent by the mentioner is enough.

Applications js to coffee

Remove assignee/milestone selects from MR form

Fixes #1079 and http://feedback.gitlab.com/forums/176466-general/suggestions/5663897-merge-request-assign-to-should-popule-with-membe

Attribution For Shell Guide

Advise In Upgrade Guide Is Outdated

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

Add gzip compression for assets to nginx example

Update user_management.md

Show emoji in autocomplete when assets gzip compression is on

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

Removes the following from test output:

  DEPRECATION WARNING: It looks like you are eager loading table(s) (one
  of: merge_requests, projects) that are referenced in a string SQL
  snippet. For example:

      Post.includes(:comments).where("comments.title = 'foo'")

  Currently, Active Record recognizes the table in the string, and knows
  to JOIN the comments table to the query, rather than loading comments in
  a separate query. However, doing this without writing a full-blown SQL
  parser is inherently flawed. Since we don't want to write an SQL parser,
  we are removing this functionality. From now on, you must explicitly
  tell Active Record when you are referencing a table from a string:

      Post.includes(:comments).where("comments.title =
  'foo'").references(:comments)

  If you don't rely on implicit join references you can disable the
  feature entirely by setting
  `config.active_record.disable_implicit_join_references = true`.

Small changes

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

Conflicts:
	doc/release/monthly.md

Suppress 'Rendered...' log messages

Mobile UI improvements

Added some extra information how a good MR looks like

Remove periods from merge request

Start development Key seed id from 1 to prevent `Couldn't find Key with id=0` crash on MySQL.

Move Project's service specs to the correct location

Update guide from 6.0 to 6.7

Move spinner for mobile

The "Merged by" and "Closed by" statements end with an extra space followed by a period. This doesn't seem necessary to me and not having the extra space followed by a period looks better to me. Also, the top of the merge request doesn't have the sentence ending with a period.

[ci skip]

ping @karlhungus

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

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