Excluded BUFFER_SIZE from commons - Added error messages in server - Renamed classes in client.

BUFFER_SIZE is now defined as DEFAULT_BUFFER_SIZE in Client and Server (because there is no dependency).
Added several error messages and removed stack-trace-prints.
Renamed several classes in client project to better distinguish same-named classes in server and client.
Excluded BUFFER_SIZE from commons - Added error messages in server - Renamed classes in client.

BUFFER_SIZE is now defined as DEFAULT_BUFFER_SIZE in Client and Server
(because there is no dependency).
Added several error messages and removed stack-trace-prints.
Renamed several classes in client project to better distinguish
same-named classes in server and client.