Added serialVersionUID to ServiceAnnouncement.
Implemented HarmonicClient.

- Modified pom.xml to build both client and server;
- Updated ServiceAnnouncement to suit the needs of carrying more information;
- Implemented Server entity that represents a Server from the perspective of the Client and implements methods for connecting to it, requesting intervals and sending intervals;
- Implemented ConnectionFailedException to isolate the rest of the application from IO and network related exceptions.