namespace: drop most boost namespaces and a few header cleanups

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

src/rpcmisc.cpp

@@ -23,7 +23,6 @@
 #include "json/json_spirit_utils.h"
 #include "json/json_spirit_value.h"
 
-using namespace boost::assign;
 using namespace json_spirit;
 using namespace std;