Update markdown reference to external issues

1. Issue may be not only in jira.
2. Rewrite method for support different external issue trackers
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 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
Remove duplicated setupNoteForm method
Updated the spring gem and fixed the guard file

Signed-off-by: Jeroen van Baarsen <jeroenvanbaarsen@gmail.com>
don't lookup branch element - it might need to be escaped
Show percentage status on milestone detail page, fixes #485
Update user_management.md

add rails_env to commands
Update markdown.rb

Fix mistake by @qqshfox report
move env to end of lines
fix link_to by @bwrsandman

Add missing '#'
Document the extra.sign_in_text setting for CE
Add rake task to drop a project's PostReceive jobs
Added AsciiDoc support and changed to singlequotes

extension to https://github.com/gitlabhq/gitlabhq/pull/7568
Tar before omnibus build, we all have master access on dev, don't forget to update installation.md
Don't forget to cherry pick into stable.