Added documentation to changed parts

src/main/java/fucoin/MainRemote.java

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

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

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

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

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

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

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