Add importer and auto-publisher: medical alerts

(cc @kalleth)

Again, to get things working on our VM, we also needed in `/app/importers/drug_safety_update_import.rb`:

```ruby
require "document_import"
require_relative "../models/builders/specialist_document_builder"
```

and in `app/lib/specialist_publisher_wiring.rb`:

```ruby
require_relative "../models/builders/specialist_document_builder"
```

Don't think these changes are needed on the live system, but tell me if I need to make them.
This will need updating to `validatable_document_factories`.