Mail Digest Cassandra repository implementation and tests

* new column family
* row key based on digest type and domain (to allow domain level
  configuration)
* subscription stored as columns
Implementation of digest email subscription at service level
GUI and Rest controller for digest emails subscription
Mail digest Service implementation
First intergation tests for email digest

* fix dataset to add domain ippon.fr
* use mockito inject to spy on call to MailService
Merge remote-tracking branch 'origin/master' into mailDigest

* Integrates evolution on mail service : use velocity templates
* Various other changes from master

Conflicts:
	src/main/java/fr/ippon/tatami/service/MailService.java
Integration tests and fixe for daily digest

* integration tests use specific users in dataset in order to avoid
  breaking other tests
* improve daily digest mail template
* fix issues found when testing
Weekly digest mail templates en integration tests

* mail template and messages for weekly digest
* partial integration tests for weekly digests
Fix cron expression for digest emails

* daily digest run monday to friday, at 22h00
* weekly digest run monday to friday, at 23h00
Merge remote-tracking branch 'origin/master' into mailDigest
Fix cron expression (do not specify year)
Add new cassandra column in migration script
Small refactoring of DigestService

* weekly digests are sent on monday for everybody
* the notion of current day is removed from the DAO and pushed to the
  Services using the DAO
* some more logs
* more comments for clarity
Merge pull request #330 from PierreRust/mailDigest

Mail digest