Split up bitcoinrpc (code movement only)

Split bitcoinrpc up into

- rpcserver: bitcoind RPC server
- rpcclient: bitcoin-cli RPC client
- rpcprotocol: shared common HTTP/JSON-RPC protocol code

One step towards making bitcoin-cli independent from the rest
of the code, and thus a smaller executable that doesn't have to
be linked against leveldb.

This commit only does code movement, there are no functional changes.

src/qt/rpcconsole.cpp

@@ -8,7 +8,8 @@
 #include "clientmodel.h"
 #include "guiutil.h"
 
-#include "bitcoinrpc.h"
+#include "rpcserver.h"
+#include "rpcclient.h"
 
 #include "json/json_spirit_value.h"
 #include <openssl/crypto.h>