Initial version of getColumnValue

Still need to (a). return the value as a Buffer rather than a string (b)
support other types (c). refactor so that it is not duplicating
ODBC::GetColumnValue needlessly.
Various changes (incomplete)

* Return Buffer for varbinary columns
* Fix SQL_T macro for compile-time string concatenation
* Fix DEBUG_PRINTF usage in ODBCConnection::Query not respecting UNICODE
flag
* Pass 3rd argument to Query callback ("more")
* Start work on GetColumnValue returning data types probably (probably
should just use ODBC::GetColumnValue somehow - needs refactoring)
* Add ODBCResult::GetColumnValueSync
Merge branch 'master' of https://github.com/lee-houghton/node-odbc