Improve jira integration doc for new version

See merge request !308

Add option for Jira cross reference mentions and fix Jira issues closing

See merge request !304

Put the call for external tracker mention in the same place as gitlab default mention. Add git push service spec.

Update the issue closing regex to count on the Jira issue mentions. Make sure push data is provided for the service.

Show asterisks if jira service user password is set. Create server url from project_url to connect to jira instance.

CE upstream

See merge request !305

Conflicts:
	app/helpers/oauth_helper.rb
	app/helpers/projects_helper.rb

GitHub importer refactoring

See merge request !1477

Submit comment on command enter

Fixes #1869.

See merge request !1474

Remove duplicates from group milestone participants list.

See merge request !1473

Gitlab.com integration && Gitlab importer

#1933

See merge request !1456

Fixes #1869.