Register INameFromTitle behavior for IBaseDocument.
Use IDocumentNameFromTitle behavior from document also for mail.
Merge pull request #311 from 4teamwork/mle-public_trial_generate_id

ftw.mail.mail has now the same ID generation mechanism.
Choose a different mail header date, since 1970... is default for DateTime and datetime (test results are nearly useless).
Add IDocumentMetadata behavior to ftw.mail.mail
Initialize metadata on mail.
Fill document_author metadata with fullname queried by email address (ogds).
Upgrade step: initialize metadata on extisting mail instances
Init missing field values in existing mails. Test metadata upgrade step.
Set delivery date on mail-out.