namespace: drop most boost namespaces and a few header cleanups

A few boost::asio were left around because they're very wordy otherwise.

src/rpcprotocol.cpp

@@ -26,7 +26,6 @@
 #include "json/json_spirit_writer_template.h"
 
 using namespace std;
-using namespace boost::asio;
 using namespace json_spirit;
 
 //! Number of bytes to allocate and read at most at once in post data