Auditing

Implemented auditing of all objects except import logs and the audit trail!
Logs 'AO:name' for action officer tokenised updates and 'SideKiq' for cron job imports
Here we have to be careful and more selective about which fields to create versions for. Devise keeps for example `last_sign_in_at`, `current_sign_in_at` and `sign_in_count` which are changed on every login. That's not kind of changes we want to keep, I suppose. 

Paper trail accepts `:only` or opposite `:ignore` option to select which fields to track. Having this one without any settings would result in a change for every login and that would flood the changes table with semantically incorrect records. 

```ruby
has_paper_trail :ignore => [:last_sign_in_at, :current_sign_in_at. :sign_in_count, :updated_at]
```