namespace: drop most boost namespaces and a few header cleanups

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

src/chainparamsbase.cpp

@@ -9,10 +9,6 @@
 
 #include <assert.h>
 
-#include <boost/assign/list_of.hpp>
-
-using namespace boost::assign;
-
 /**
  * Main network
  */