Added support for the BIT type

- Moved socket_connection to a separate include file.
- Clarified Stream requirements.
- Made make_error_code public.
- Updated include styles to match Boost's.
- Moved <boost/myql/mysql.hpp> to <boost/mysql.hpp> to match
conventions.
- Added support for the BIT type.

closes #13
closes #21

test/integration/network_functions/sync.cpp

@@ -35,7 +35,7 @@ class sync_errc : public network_functions<Stream>
     static network_result<impl_result_type<Callable>> impl(Callable&& cb)
     {
         network_result<impl_result_type<Callable>> res (
-            boost::mysql::detail::make_error_code(errc::no),
+            boost::mysql::make_error_code(errc::no),
             error_info("error_info not cleared properly")
         );
         res.value = cb(res.err, *res.info);