Several structs added, macros for colored printing, welcome messages and arguments handling

Added following structures:
- clientInfo : deals with the connection. Let the server have data (pid, name) about the client
- clientMessage : message client -> server. Contains message type and content (client can this way tell he's leaving)
- serverMessage : message server -> client. Contains message type and content (server can kick client, tell him the time left, tell him if the number is higher or lower than the previous proposition by the client)