Basic forum sections, ad images, and time to post calculation 

Three fixes:
1. Donation, facebook and twitter images had the wrong name on clean installation (missing 'ad' prefix).
2. Basic forum sections where added to the clean database during installation so that forum issues would be easier to work on.
3. When submitting two posts in under than 15 seconds, the error message returned the wrong number of seconds when the database timezone and the local machine timezone are different. Move the calculation to the database.