Cleanup deprecated functionality

[dveeden]

See also: #415

This removes:

Admin functions (e.g. createdb, shutdown, dropdb, reload). The commands in the protocol have been removed and have been replaced with regular SQL.

$drh->func('createdb', 'admin', '127.0.0.1:3306', 'root', 'xxx', 'admin');

Support for LISTFIELDS. Use SHOW COLUMNS... instead.

$dbh->do('LISTFIELDS t1');