Bootstrap DynamoDB tables before loading Spring context.
Add BridgeEncryptor and a bean "healthCodeEncryptor".
Phase out table "HealthCodeSalt".
Add data objects HealthId and HealthCode.
Should share the DynamoDB client across threads thus removing the "prototype" scope.
Add DynamoHealthCodeDao.
Make deleting table more robust.
Add HealthIdDao.
Add HealthCodeService.
Merge pull request #79 from eric-wu/develop

Further implementation of the new security strategy