Tons of fixes

Fixes for this pull request:

1) Set mysqli as the default driver and updated the hard-coded code in the installer to use the mysqli.db.php class instead of the mysql class.

2) Removed the mysql option as it is now deprecated. Also, I set the installer to check if the server uses PHP 5.3+ instead of 4.3. You can change that to 5.2 if you want, although it isn't recommended considering other forums use 5.3 as the minimum PHP version.

3) Fixed those illegal offset errors on the headers.

4) Fixed timer.inc.php (should be timer.php) on the migration scripts.