elk_db_replacement__callback seems to be useless unless it was maybe there for backward compat?

Signed-off-by: emanuele <emanuele45@gmail.com>
Goodbye Db-{type}.subs.php, a long time ago you were necessary, now I can't find any useful reference

Signed-off-by: emanuele <emanuele45@gmail.com>
Some db may require password confirmation when creating an admin account at install, others not
Fixed Postgre mimic of INSERT REPLACE and affected_rows - should fix #974

Signed-off-by: emanuele <emanuele45@gmail.com>
Destroy all the possible sessions at logout?

Signed-off-by: emanuele <emanuele45@gmail.com>
Casting id member in setLoginCookie and fixed the cookie validation regexp accordingly

Signed-off-by: emanuele <emanuele45@gmail.com>
Merge pull request #985 from emanuele45/db_class

Some love for the db layer