Poweradmin innodb conversion

Edmondas, 

This change makes PowerAdmin work with InnoDB alone, a much better
option in terms of data-safety and database management.

Please don't blindly merge it. I don't know much about PHP and it is possible that I've committed mistakes in my change. I trust your keen eyes and knowledge of the code will help spotting those.

Please let me know if you have other database-related issues, I am glad to be able to help.

Kind regards,
--
LMC

UPDATE: omitting two files and one useless line as per Edmondas' comments.