Implemented futures for receiving the supervisor

src/main/java/fucoin/Main.java

src/main/java/fucoin/actions/join/ActionJoin.java

src/main/java/fucoin/actions/join/ActionJoinAnswer.java

src/main/java/fucoin/actions/join/ServerActionJoin.java

src/main/java/fucoin/supervisor/SuperVisorImpl.java

src/main/java/fucoin/wallet/AbstractWallet.java

src/main/java/fucoin/wallet/WalletImpl.java