Import the database as the `git` user

This ensures that all tables created during the import belong to `git`.
If you import as a different user, such as the `postgres` superuser, you
may encounter issues where the GitLab database user cannot access tables
in gitlabhq_production, _even if_ `git` is the owner of
gitlabhq_production at the time of import.
Update markdown reference to external issues

1. Issue may be not only in jira.
2. Rewrite method for support different external issue trackers
prevent events loading while loading events refs #49759
Delete mailer queue because we don't use sidekiq_mailer gem and now the mailer queue doesn't exist any more.
change bash to sh
fix bash-ism
Fix milestones description's max length
Fix 404 error when clicking the branch link on hipchat message
Include "Merge-request reopened" emails in the proper email thread
Fix missing links and incorrect display of issue numbers for notes, comments, and merge requests
Moved padding from li to a in dashboard groups / projects listing
Removed redundant spans
# This is a combination of 2 commits.
# The first commit's message is:

Patched `MergeRequest` to return more data.

Patched `MergeRequest` to return the `description` & `milestone`
Conflicts:
	lib/api/entities.rb

# This is the 2nd commit message:

Update merge_requests.md

Update documentation for merge request endpoint adding support for description.
Patched `MergeRequest` to return more data.
Added milestone to merge_requests instead of milestone id.
Remove duplicated setupNoteForm method
Rtrim input before checking if form is empty
Add dealing with newlines for editor to 5.1-to-6.0

backport of https://github.com/gitlabhq/gitlabhq/commit/2d681c0d1ed14bf23c041aa04fa3e77caceda9a1
add git config --global core.autocrlf check

core.autocrlf was added to install guide in https://github.com/gitlabhq/gitlabhq/commit/2d681c0d1ed14bf23c041aa04fa3e77caceda9a1 but not added to check script
Move LDAP timeout code to Gitlab::LDAP::Access
Cache LDAP check in Gitlab::UserAccess

This changes the number of LDAP calls when users access GitLab via
Git-over-SSH or the API. LDAP check results are cached for 1 hour.