bitcoin-cli: remove unneeded dependencies (only code movement)

Remove unnecessary dependencies for bitcoin-cli
(leveldb, berkelydb, wallet, RPC server)

Build system changes:
- split libbitcoin.a into libbitcoin_common.a, libbitcoin_server.a and
  libbitcoin_cli.a

Code changes (movement only):
- split up HelpMessage into HelpMessage in init.cpp and HelpMessageCli
  in rpcclient.cpp
- move uiInterface from init.cpp to util.cpp

src/init.h

@@ -26,8 +26,7 @@ bool AppInit2(boost::thread_group& threadGroup, bool fForceServer);
 enum HelpMessageMode
 {
     HMM_BITCOIND,
-    HMM_BITCOIN_QT,
-    HMM_BITCOIN_CLI
+    HMM_BITCOIN_QT
 };
 
 std::string HelpMessage(HelpMessageMode mode);