[enh] Upgrade to elasticsearch 2.4.5

- Client: transaction options ar now optional (ask in prompt)
- Network peers : filter on currency, to evict bad currrency peers

- Core  : entities currency and peer model use String for ID
- ES : add new DAO classes
- ES : Code refactoring to an extended Client

 - Remove guava dependency (in modules core-client and core-shared)
 - Remove gson (keep as optional in module core-client)
 - Add /node/summary Rest action

- Add user event on blockchain changes