Database fixes, additions and such

Fixed database connection, finally decided which database model I'll be
using. I was thinking of PDO MySQLi but I found so much problems with
the model in this project I'm doing (+ my lack of knowledge), so that I
went for basic MySQL.

Added topic class, updated database class and few things to index file.
Also added jQuery library in already (it's a default script, so it's
placed into forum/scripts instead of themes/.../js).

Going to figure out the display of forum components next.