Implement Beeswax functionality in impyla

Abstract out Connection and Cursor to have subclasses for HiveServer2
and Beeswax. User can specify the type of connection through the added
protocol parameter in connect.

HiveServer 2 also supports retrieving summary and profile.
Delete these constants.  Just use magic numbers.  (Not usually a proponent of this, but don't want to give unnecessary weight to CM port numbers.)