utils dbi: Added initial version.

This module provides helper functions for using libdbi. Currently, data types
and functions for managing connection options, a database connection as well
as a generic query helper are available.

The query helper (sc_dbi_exec_query()) uses a specified callback function to
handle each row as returned from the SQL query. A custom data-type (based on
the libdbi data-types) is used to pass the query results to the handler
callback.