Add Event Log for troubleshooting signon issues
Add event logging in controllers and user model
Add event log viewing to the front end
Limit events to the newest 100
Tidying up UI for editing users and viewing logs
Avoid errors before calling `User.find_by_email`
Use factory default names
Integration tests for admin role permissions.

Organisation admins can see the account access for users in their organisation
Passphrase expired event no longer registered twice
Rename event to MANUAL_ACCOUNT_UNLOCK
Merge pull request #227 from alphagov/event-logging

Event logging