Clarify label of alternative format email address input field

* Changed for edition editing - applied to all editions and not just
  "news" and "detailed guide" that are mentioned in the story.
* Changed for organisation show & form in admin

https://www.pivotaltracker.com/story/show/45974277
Merge pull request #722 from alphagov/alternate-email-label

Clarify label of alternative format email address input field

https://www.pivotaltracker.com/story/show/45974277
Update 'Upload from Zip file' copy

https://www.pivotaltracker.com/story/show/54359834
Add logstasher Gem
Custom @fields.request format to match Nginx logs
Protect against LogStasher not being defined
Clarify @fields added
"View" button on published documents to open in new tab

https://www.pivotaltracker.com/story/show/54468890
update schema
Fix report a problem margin on mobile
Merge pull request #725 from alphagov/application-logs-in-logstash-format

Application logs in logstash format
Merge pull request #726 from alphagov/report-a-problem-mobile-margin

Fix report a problem margin on mobile