Small bug fixes.

Removed references to Prettify which was removed from the core.
Also fixed edit_post get_categories that was passing an unexisting
parameter, from when the database was still accessed with mysqli.
Changed the create_database post_date to date instead of datetime.
Changed the cookie duration to 604800 in config.
Merge branch 'master' of https://github.com/KaivoAnastetiks/KALab