This implementation has a slim server. The main objective is to build a entermidiate version between the fatServer and the implementation without server at all.

- added some properties in the PDUs.
-- the objective is to reference a specific userId as the receiver of that PDU.

- removed a lot of code from the server

-- the server keeps track of the clients registered
-- registers users
-- send unicastPDU to a given user
-- send broadcastPDU
-- TODO: unregister users when receiving a unregisterPdu
the spam contoll is now done on each android client
libs
Merge remote-tracking branch 'refs/remotes/origin/fatClient'
- the server has a very simple implementation
-- the main objective of the server is to register users and know how to send them messages
- the client does all the remaining work