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/bitcoin-cli.cpp

@@ -42,7 +42,7 @@ static bool AppInitRPC(int argc, char* argv[])
               "  bitcoin-cli [options] help                " + _("List commands") + "\n" +
               "  bitcoin-cli [options] help <command>      " + _("Get help for a command") + "\n";
 
-        strUsage += "\n" + HelpMessage(HMM_BITCOIN_CLI);
+        strUsage += "\n" + HelpMessageCli(true);
 
         fprintf(stdout, "%s", strUsage.c_str());
         return false;