General fixes

[Guergeiro]

Fixed #17!

• In one of the pull request I mistakenly swapped the way replicas are added to the ConcurrentHashMap.
  • In PlaceManager.addReplica() was using replicas.replace(FullAddress, Date) and should be using replicas.put(FullAddress, Date).
  • The .replace implementation doesn't add a <k,v> if doesn't exist.
  • This meant that replicas.size() was always 0 so, the server would always get the majority since it voted for himself. 1 > size [0] / 2 == true, always.

Changed how starting the server works

• Server now expects 4 arguments (was 3 before).
  1. Multicast Address
  2. Multicast Port
  3. Server Address (normally 127.0.0.1)
  4. Server Port
• Updated Dockerfile to account for these changes.

File restructure

• Swapped ComunicationMessage to ComunicationHeartbeat everywhere ComunicationMessage was referenced.
• Updated serialVersion of Serializable objects.
• Changed PlaceManager.newTimeout() to receive the min and max timeout possible values.
• Removed synchronized from methods that used to access ConcurrentHashMap of PlaceManager, since concurrency is already handled at class level, and adding another level lock is, not only ambiguous, but also potentially harmful.

JavaDocs

• Updated JavaDocs.

[Guergeiro]

@EdwinOliveira and @stephs10, all .html and .js file do not need to be reviewed.