general fixes, fixed database prefix during install

[0xRenegade]

Fixes:

• Missing scrollbar on sidebar inside /documentation/ folder
• Option exists for database prefix but doesn't work; this adds in that feature.

[0xRenegade]

@giandonatoinverso I noticed you closed the issue #30 after submitting this. Would you like to close it or would you welcome this feature?

Codacy errors have to do with Getenv() use and #prefix# bugging out the sql file checks. Other than that it's tested and works with+without prefixes.

EDIT: Nevermind, tested again and it seems i wasn't hitting some of the more manually entered queries from the database class's query function.

[0xRenegade]

Fixed this up after testing again, there were manually entered queries inside some lib (model) files, as well as index.php. The manually entered ones using $db->query() don't take into account the self::$prefix that is set inside class normally, because the queries aren't prepared.

[giandonatoinverso]

well done! thanks