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
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 current sign-in date

add current sign-in date to admin section profile view
add missing config files to check during release process
Adding in snippet search functionality

http://feedback.gitlab.com/forums/176466-general/suggestions/5529795-search-though-snippets
Fine-tune the Remove Project redirect. Now it redirects to admin_projects_path and shows a flash message confirming the action has been taken.
change git to git bin path
Add permalink to fixed SHA URL on blob view.
Fix missing to on reassign MR email to unassigned.

Factors out MR and issue email.
added str-truncated to branch list to fix issue #7192
update repo recreation details
Changing some formatting for the Hound, modifying some UI text
Fix missing to on reassign MR text email to unassigned.

Factors out text MR and issue email.