Remove the primary components of the TagMessenger
Changing DAOs and DBOs to use a modified ObservableEntity and the TransactionalMessenger
Revert the rename of eTag to etag for a few classes
Also remove some deprecated code from V2 migration
Replace EtagGenerator with UUID.randomUUID().toString()
Remove forceEtag booleans and any remaining CRUD from migration v2 backups (i.e. unused code).
Merge pull request #877 from kaysoky/TagMessengerRefactor

Factor out TagMessenger and EtagGenerator and (deprecated) CRUD from backup